- John Hadley (1682-1744) built the first good reflecting telescope, in the Gregorian form, in 1721 or 1726. This had a 6 inch diameter and a focal length of 62 inches. He presented it to the Royal Society, where it was compared to Huygens' 125 ft focal length refractor and found to be as good and vastly more convenient. He made a number of other telescopes. . A 1971 booklet on the Science Museum says this telescope is in the Museum, but I don't recall seeing it there. He invented the octant in 1731 and patented it in 1734. This was rapidly developed into the modern marine sextant. I don't know if he had any London connections -  says he was a country squire. Hooke had suggested an octant in 1666. Newton had exhibited such an instrument in 1699 but had not developed it. Halley also had a similar design. A Philadelphia glazier, Thomas Godfrey, developed a quadrant in 1730 and the Royal Society gave him £200 in recognition of his priority. The sextant rapidly displaced the mariner's astrolabe. Good observers differ by only a minute in measuring the sun's meridian altitude.
- Philip Hall (1904-1982) was born in Hampstead and lived at 8 Well Walk from 1911 to 1927, when he was elected a Fellow of King's College, Cambridge, but he considered this his home until his mother moved to Cambridge in 1948. In early 1927, he worked for some months with Karl Pearson at University College London on the tables of the Incomplete Beta Function.
- Edmond Halley (1656-1742), was born on 29 Oct 1656 (OS) in Haggerston Road, Hackney, north London, the son of a rich soap boiler . He went to St Paul's School (now removed to Barnes in south west London). At Oxford in 1673-1676 and then catalogued southern stars on St Helena for a year - published as Catalogus Stellarum Australium in 1679.  notes that the atmosphere in St Helena was not good and Halley found only 341 new stars. FRS, 1678. Settled in Islington in 1682 and built an observatory there.  says he moved from Islington to Golden Lion Court, Aldersgate Street, upon his marriage in 1682.
Gets Newton to write the Principia, and subsidises its publication, 1684-87. Assistant Sec (or Clerk) RS and editor of the Phil. Trans. in 1685-1693.  Clerk to the RS, 1686-1698. Discovered the thin lens equation, c1692. 1693 - makes first life tables for insurance. 1701 - publishes first chart of magnetic variation after commanding a navy exploration ship in the Atlantic for a year. He then surveyed the Channel and then the Adriatic. He succeeded Wallis as Savilian Professor of Geometry in 1704. Sec RS, 1713-1721.
He made a detailed study of the eclipse of 1715, asking informants to detail exactly what they had seen and from where. In recent years this data was re-examined and allowed the path of totality to be determined to within a few miles and demonstrating that the sun has not changed size in that period. He rediscovered the saros, the cycle of 223 lunar months of the precession of the moon's orbital plane with respect to the earth's orbital plane. It had been known to the Babylonians and the Greeks, but apparently had been overlooked. Hipparchos had used it to determine the length of the year to within a few minutes.  Demonstrates a diving bell in the Thames in 1716. Discovered the proper motion of stars in 1718, showing that some stars had moved by a degree over 2000 years. He became second Astronomer Royal in 1720, succeeding John Flamsteed. In 1720, the 64-year Halley started on a 18-year cycle of observations of the moon, which he completed! Predicted the Transit of Venus in 1769 which led to Cook being sent to Tahiti to observe it.
He was buried beside his wife in St Margaret's, Lee, churchyard, about a mile south of Greenwich. (In 1836, John Pond, sixth Astronomer Royal, was buried in the same place.) In 1854, the Admiralty restored the tomb but the original tombstone was removed to the Old Royal Observatory at Greenwich , where it can be seen in the courtyard. 
- Thomas Harriot (or Harriott) (1560-1621), the early algebraist and astronomer, inventor of the signs < and > (in somewhat different forms), was navigational tutor to Sir Walter Raleigh and his sea captains. In 1585 he went to Virginia and made the first survey of it. While there, he was the first English traveller to record an Indian language, Algonkin, creating a phonetic alphabet and compiling a dictionary. On his return from Virginia in 1585 or 1586, Harriot is said to have been in charge of the consignment of potatoes brought from Peru by Drake and hence was responsible for distributing them in Britain and Ireland. His A briefe and true report of the new found land of Virginia of 1588 was one of the earliest descriptions of any part of North America.
He was part of the household of Henry Percy, ninth Earl of Northumberland (1564-1632), from about 1588 (or 1598). The Earl was a notable patron of learning, known as the 'Wizard Earl': Thomas Allen (qv), John Dee, and Nathaniel Torperley were friends and regularly met with him. The Earl was suspected of being part of the Gunpowder Plot in 1605 and spent the next 16 years imprisoned in the Tower where the group met regularly. They were generally known as 'Henry and his three Magi' - though I'm not sure which the three were -  say they were Harriot, Walter Warner and Thomas Hughes. Raleigh, Harriot, Christopher Marlowe and the Earl were named 'The School of Night' by Shakespeare . The earliest known English globe, by Emery Molyneux in 1592 and believed to have been presented by Raleigh to the Earl while they were both in the Tower, is at Petworth House, West Sussex.
Harriot lived at the Earl's country house, Syon House (now in suburban west London), from 1607 (or 1598) until his death. He used a telescope there from c1609, making observations before and contemporaneously with Galileo, (he made a map of the moon some months before Galileo began observing ), but he did not have Galileo's passion to communicate his results and our knowledge of what he did is relatively recent. He may have been the first person to observe sunspots in modern times, c1610. He noticed the moons of Jupiter and calculated their periods. He found the sine law of refraction c1601, some twenty years before Snell.
He died at the house of Thomas Buckner in Threadneedle St He was buried in the church of St Christopher le Stocks in Threadneedle St His monument was destroyed in the Great Fire. The site was taken over by the Bank of England in 1781 . Jon Pepper says all the remains in the church were then translated to Nunhead Cemetery in south London, but he hasn't got the vault numbers to hand. In 1971, a commemorative plaque, bearing the original wording of the destroyed monument, was placed inside the Bank of England, to the left of the main door, about where the church was. Unfortunately the public is not admitted at the main door, but if you ask at the Bank of England Museum (entrance in Bartholomew Lane) or telephone the Bank, you may be shown the plaque. Walter Warner edited Harriot's algebraic writings as Artis Analytic Praxis ... some years after his death, but much of his work remains in manuscripts in the British Library.
- John Harris (1666?-1719) was a clergyman, topographer, scientific writer and private teacher of mathematics. He compiled the first English dictionary of arts and sciences. FRS 1696. About 1698, he started giving free public lectures on astronomy and mathematics at the Marine Coffee House, Birchin Lane, EC3. Secretary of the RS in 1709-1710. He was one of the first writers of academic textbooks in mathematics and astronomy. (There was a Joseph Harris (1702-1764), astronomer and mathematical instrument maker, who taught mathematics at Crane Court, off Fleet Street and became Assay Master at the Mint in 1748. He seems to be the son of John as he edited later editions of John's works.)
- John Harrison (1693-1776) invented the marine chronometer, "the greatest single aid to navigation", which solved the problem of finding longitude. After various visits (see G. Graham, above), he moved to London about 1740 to complete his H2, finished in 1741. Copley Medal RS, 1749. H3 completed in 1757. In working on H3, he invented the bimetallic strip and developed ball bearings. In 1753, a skilled London clockmaker named John Jefferys made a pocket watch (now in the Clockmakers' Company Museum, qv) for Harrison under his supervision and incorporating many of his ideas. The success of this inspired H4. H4 completed in 1759. In H4, he used diamond bearings, though it is not known how he developed the necessary technique. Unfortunately, the Astronomers Royal of the time were committed to the method of lunar distances and strenuously resisted Harrison's claim on the Longitude Prize - Maskelyne seems to have deliberately sabotaged both the tests and the actual chronometers.
Harrison lived at Summit House, Red Lion Square at the corner of Dane St, now an office block, from 1752 until his death there (Blue Plaque) . It was here, on 14-19 Aug 1765, that a committee, including John Bird, N. Maskelyne, the Cambridge mathematicians William Ludlam and John Michell, and the clockmakers Thomas Mudge and Larcum Kendal (formerly apprentice to Jefferys), was shown the detailed construction of H4, leading to Harrison finally receiving half of the Longitude Prize. After further trials, considerable opposition and even sabotage by Maskelyne and an appeal to the King, Harrison was awarded a further 8750 by Parliament in 1773, but the Longitude Act was revised to be so demanding that the prize was never claimed! Kendal made a replica of H4 and two simpler versions. Mudge made three chronometers, though Maskelyne managed to break the first one of them, and received 3000 from the Board of Longitude. John Arnold was the first to mass produce chronometers, though his first three performed poorly on Cook's second voyage. Thomas Earnshaw made further simplifications, including the spring detent escapement which needed no lubrication. The competition between Arnold and Earnshaw brought prices well below 100 with pocket versions being even less. In 1805 Arnold's son and successor and Earnshaw were both awarded 3000 by the Board. H1 - H4, K1 - K3 and examples of Earnshaw's and Arnold's work are in the Royal Observatory (qv), along with much related material.
Harrison is buried in the churchyard of St John, Hampstead, in Church Row, just south of the church, with a long inscription describing his works, though he had no known Hampstead connection. His wife and his son William (1728-1815), who worked with his father and assisted with the chronometer trials, are buried in the same tomb. When friends proposed the father for the FRS, he declined and asked for William to be elected, which he later was, in 1765. The tomb has been several times restored by the Clockmakers' Company.  Portrait in the Royal Observatory.
- John Harvard (1607-1638) was born in Southwark and christened at St Saviour's (Southwark Cathedral). Student at Emmanuel College, Cambridge, in 1627-1635. In 1637, he went to Massachusetts and left 800 (= $2000) and his library of 320 books to a new college which was later named for him. His family owned the Queen's Head Inn, formerly at 103 Borough High Street, (Southwark plaque) ;  and I recall that the proceeds of the sale financed Harvard in the New World.  implies that the inn belonged to his wife's family. Commemorative chapel and window in Southwark Cathedral.
- John Hawkins (d. 1694), who edited (or cobbled?) Cocker's Arithmetick for publication in 1678, after Cocker's death, was also buried in St George the Martyr. (See Cocker above.)
- Oliver Heaviside (1850-1925) was born at 55 King Street (now Plender Street), Camden Town. His mother's sister had married Wheatstone. His mother had been a governess to the Spottiswoode family and may have taught Spottiswoode. She set up a school at their home in 1855 and Oliver attended. The school closed in 1862. Oliver attended Camden House School in the area in 1858-1865. The family moved to 117 Camden Street in 1863. After school, he spent two years in private study and then six years with the Great Northern Telegraph Company (or the Anglo-Danish Telegraph Company) at Newcastle, which position was probably due to Wheatstone's help. Having learned all there was to know about telegraphy, he retired(!) to the family home for the next 23 years. In fact, before leaving Newcastle, he had published seven papers, including new methods for duplex telegraphy. They moved to 3 St Augustine's Road in 1876 and then to Devon in 1889.
By 1873, he had mastered calculus and differential equations and in 1873, he discovered Maxwell's work which he was among the first to master, already applying it in 1876. At this time, the invention of the telephone posed a whole new range of problems - an underground telephone line of four miles length produced so much distortion as to be impracticable - so he began studying the role of inductance. Thomson/Kelvin had developed a theory of propagation in cables in 1855, but this ignored self-inductance and gave a form of the diffusion equation, which predicts different rates of propagation for signals of different frequencies and a time of propagation proportional to the square of the distance, giving rise to the disastrous distortion and great delay observed, though Thomson was able to make the Atlantic Cable usable since only low frequencies were used. In 1876, Heaviside took account of self inductance, obtaining the equation of damped harmonic motion known as Heaviside's Equation of Telegraphy. This showed that the introduction of self-inductance could diminish the damping factor and lead to a form of the wave equation, which predicts propagation of all frequencies at the speed of light in the cable. This work was contrary to the opinions of W. H. Preece, the Chief Electrician of the Post Office, and led to Heaviside's reports being actively suppressed. In the US, Michael Pupin used Heaviside's theory to correct the distortion - he was able to patent this and made a fortune from it.
In 1885, Heaviside was the first to present Maxwell's equations in their present form. He used the scalar and vector products but otherwise abandoned quaternions. In 1889, he first gave the basic equation for the motion of a charge in a magnetic field - possibly the first occurrence of the newly discovered charged particle in electromagnetic theory. Most of his publications were in The Electrician and hence were little noticed by academics, but experimentalists began verifying his results and Thomson/Kelvin praised his work to the IEE in 1889. Oliver Lodge proposed him for the Royal Society and he was elected, despite some reservations, in 1891. His Electrical Papers appeared in two volumes in 1892. In 1894, Fitzgerald, Lodge and Perry tried to get him to accept a grant from the RS Relief Fund but he would not accept it. However, in 1896, the same friends, supported by Rayleigh and Kelvin, got a Civil List Pension of 120 per year for him.
In 1899, Fitzgerald asked him about electromagnetic wave propagation around a sphere, which Marconi's experiments showed to occur. In 1901, Heaviside and A. E. Kennelley noted that the sea was a conducting layer, as was the earth to a lesser extent, so that if there was a conducting layer in the atmosphere, then electromagnetic waves would be guided between them to circle the earth. Heaviside made these observations in his article on 'Telegraphy, Theory' in the 1902 supplement to the Encyclopaedia Britannica. The Heaviside Layer (or Ionosphere) was found to exist and explained why Marconi's wireless telegraphy works. His Electromagnetic Theory appeared in three volumes in 1893, 1899 & 1912. He declined the Hughes Medal of the RS in 1904. PhD honoris causa from Gttingen in 1905. Hon. Mem. IEE in 1908; Hon. Mem. American IEE in 1918. In 1923, the IEE awarded him its first Faraday Medal and the PIEE travelled to Torquay to present it to him.
Heaviside was the main promoter of the 'rationalized MKS system' of electromagnetic units - in these a factor of 4π is put into a few basic equations where it naturally relates to the surface area of a sphere and this eliminates it from many equations where it mysteriously occurred. After Lorentz adopted it some years later, it became the standard system. His work was a major factor in the development of vector analysis, in opposition to quaternion methods. Heaviside also developed the operational calculus, now partially formalised in the standard theory of Laplace transforms, though Heaviside's approach is considerably more sophisticated and general. He also studied the speed of light and deduced the denominator of some fifteen years before Einstein. In his years at Devon, he lived as a recluse, never attending any scientific meetings and even refusing to see visitors. After 1916, he lived alone, becoming even more reclusive than previously - he was frequently behind with his rates (property taxes) and his gas was cut off several times, once for 15 months. See also: Science Museum. ; ;  See also under Newton Abbot, Paignton and Torquay.
- John Hellins was the son of a labourer and was apprenticed to a cooper. He taught himself mathematics, became a schoolmaster and then an assistant at the Royal Observatory. FRS in 1796. His paper "An improved solution of a problem in physical astronomy; by which swiftly converging series are obtained which are useful in computing the perturbations of the motions of the Earth, Mars and Venus ...", Phil. Trans. (1798) 527-566, won him the Copley Medal of the Royal Society. He later took holy orders.
- George Wirgman Hemming (1821-1905), a law reporter who also published work on calculus, lived at 3 Fairfax Road, South Hampstead, and is buried at St John, Hampstead .
- Thomas Archer Hirst (1830-1892) lodged with John Tyndall in a house formerly belonging to T. H. Huxley, 1860-1869. He died at Oxford & Cambridge Mansions (since renamed), Marylebone Road. He is buried in Highgate Cemetery.  (Robin Wilson gave a talk on Hirst to the BSHM on 29th June 2002 at Greenwich - TM)
- Thomas Hood (fl. 1577-1596). Thomas Smith, see below, founded the first English lectureship in mathematics in 1582 with Hood as the first lecturer, lecturing in Staples Inn Chapel and in Smith's house.  I have a note saying the lectures started in 1588. Published a book on The Use of the Celestial Globe in Plano, set forth in two hemispheres in 1590 which discussed the nova of 1572. Popularised astronomy and the Copernican theory. Lived in Abchurch Lane, from which he sold copies of his hemispheres.
- Robert Hooke (1635-1703) came to London in 1648 and worked for Sir Peter Lely. Student at Westminster School.
1658, Describes the balance spring for watches and apparently made some watches using it.
1662, Curator of the Royal Society, expected to produce new experiments and devices on a regular basis. This gave him rooms in Gresham College. FRS, 1664.
1665, Micrographia, the first book on microscopic observations. Coins the word 'cell'. Suggests freezing point of water as zero point for thermometers. Conjectures that some constituent of the air is necessary for combustion and breathing, but this had no influence.  First points out the colour phenomenon known as Newton's rings (giving a quasi-explanation) and the black spot in soap bubbles. Gives theories of light and heat. Describes the invention of the compound microscope and suggests immersion lens. Explains twinkling of stars.
1665, Gresham Professor of Geometry, until 1703.
He was one of the City Surveyors after the GF. 
1670, states, in the first Cutlerian lecture, An Attempt to Prove the Motion of the Earth from Observations, to RS, the law of gravity, but without the inverse square term - though he added this later. However, he could not prove anything about it. Cutler apparently never paid the funds promised.
1674, Animadversions ... describes Hooke's invention of the universal joint and the clock driven telescope.
1670-1679, designed the church of St Edmund the King and Martyr, Lombard Street at Birchin Lane.
1676, A Description of Helioscopes ... describes Hooke's invention of the balance spring watch. c1675, he also invents the anchor or recoil escapement, which makes the pendulum clock much more usable and accurate and is still in common use (though this also is attributed to a William Clement). The helioscope probably inspired Hadley to invent the octant.
1677-1682. Secretary of RS. Produced seven numbers of the Philosophical Collections for the RS in 1679-1682, when the Phil. Trans. was interrupted by Oldenburg's death.
1678, Lectures de Potentia Restitutiva, or of Spring ... gives first statement of Hooke's Law, which he phrased as 'Ut tensio sic vis', but presented as an anagram: ceiiinossttuv.
First to observe that falling barometer indicates bad weather, to build a Gregorian telescope, to show that Mars and Jupiter rotated (being the first to observe the Great Red Spot of Jupiter), to observe that the tail of a comet was repelled by the sun, to invent the iris diaphragm, to note that movement where the restoring force is proportional to the displacement gives simple harmonic motion, to observe Chladni figures.
1696. Health breaks down. He died at Gresham College. ; 
Buried in the chancel of St Helen's, Bishopsgate, close to where Gresham College was . However, there was never a monument until the late 19C when a stained glass window was erected. Sadly it was destroyed in the IRA bombing in 1992 and no colour picture is known. The caretaker provided a picture from The Sphere (23 Feb 1935) 268ff. Perhaps the Royal Society should erect a monument, perhaps on the 400th anniversary of his death.
One of his descendents, William (1751-1819), a painter, is buried at St John, Hampstead . There is a gazebo in the front garden of The Grange, 52 Crooms Hill, Greenwich, which was designed by Hooke in 1672 for Sir William Hooker, Lord Mayor of London ; .
- Godfrey Hounsfield (1919- ) was working at the EMI Central Research Laboratories in Hayes, London, when he developed computer-assisted tomography (CAT) - Nobel Prize in Physiology or Medicine, 1979.
- Edmond Hoyle's book on whist first appeared in 1742. Little is known of him except that he died on 29 Aug 1769 in what is now Welbeck Street and is said to be buried in Old St Marylebone church, marked by the present Garden of Rest in Marylebone High Street .
- Charles Hutton (1737-1823) lived in Bedford Row after his retirement from the Royal Military Academy in 1807 and died there. He is buried in the family vault in Charlton churchyard, near Woolwich. . 
- Constantijn Huygens Jr. (1628-1697), elder brother of Christiaan, followed in their father's footsteps as secretary to the rulers of the Netherlands. When William of Orange became William III of England, Constantijn spent most of his winters in London - summers were spent fighting the French in southern Netherlands. Constantijn and Christiaan had developed the grinding of large lenses in 1682-1687, making about 40 lenses, with Constantijn producing producing most of the long focal length examples. In 1690, the Royal Society asked Constantijn for an example and he brought them one of focal length 122 ft with his signature. In 1725, the Society acquired the two examples of longest focal length, both by Constantijn - cf under Royal Society. 
- James Ivory (1765-1842) retired from the Royal Military College, Marlow (later Sandhurst), in 1816 due to ill-health, which may have been mental problems. He moved to London and lived a recluse until his death.
- William Jones (1675-1749) came from Anglesey to London as a young man. After maritime service, he set up as a mathematics teacher in 1702. New Compendium of the Whole Art of Navigation, 1702. His 1706 Synopsis palmariorum mathesos, or A New Introduction to the Mathematics introduced the symbol for what we now denote by π and first published Machin's calculation of π to 100 decimals. This work attracted the the attention and friendship of Newton and Halley. Tutor to the 1st and 2nd Earls of Macclesfield (the 2nd was later an astronomer involved in the adoption of the Gregorian calendar and PRS), living at their Shirburn Castle, Tetsworth, Oxfordshire. Deputy-teller to the Exchequer. Edited and published a compilation of Newton's smaller works: De Analysi, Quadratura Curvarum, Enumeratio Linearum Tertii Ordinis and Methodus Differentialis in 1711. Member of the RS committee to determine the originator of the calculus in Mar 1711. FRS, 1712. Later VPRS. In 1737, he had a house next to the Salt Office in York Buildings. His son, Sir William Jones (1746-1794) was a linguist and jurist at Calcutta, India. 
- Friedrich August Kekul (von Stradonitz) (1829-1896) was one of the principal chemists of the 19C. As a young man, he was an assistant chemist at the Mint and lived in Clapham, about 1854-1856. Years later, he related the following. "During my stay in London I lived for a long time in Clapham Road, near to the common. I often spent the evenings with my friend Hugo Mller in Islington, at the opposite end of that vast town. There we talked about many things but most often of our beloved chemistry. One fine summer day I was riding once again on the last omnibus through the deserted streets of the metropolis, at other times so crowded - 'outside', on the roof of the omnibus, as usual. I sank into a day-dream. There before my eyes gambolled the atoms. I had always seen them in motion, those tiny beings, but I had never succeeded in discerning the nature of their motion. This day I saw how frequently two smaller atoms joined themselves together like a loving couple; how larger ones embraced two smaller ones, how still larger ones seized three and even four of the smaller ones, and how the whole twisted in a whirling dance. I saw how the larger ones formed a line and dragged along still smaller ones at the ends of the chain. I saw what our past master Kopp, my highly respected teacher and friend, described to us in such a delightful manner in his 'Molecularwelt', but I saw it long before him. The cry of the conductor 'Clapham Road' roused me from my musings, but I stayed up part of the night in order to commit to paper at least the outlines of that vision. In this way began the structure theory." Kekul's vision and notation helped lead to the present chemical notation within a decade. He showed carbon was tetravalent in 1858. He is even more famous for a later dream, gazing into a fire in Ghent, Belgium, in 1865, when he visualized the hexagonal ring structure of benzene, described as 'the most brilliant piece of prediction in organic chemistry'.  The development of chemical diagrams was an important impetus to the development of graph theory. FRS, 1875. Copley Medal, RS, 1885.
- Alfred Bray Kempe (1849-1922) was born and died in London. Though he studied mathematics at Cambridge, he went into Ecclesiastical Law. But he retained an interest in mathematics, publishing How to Draw a Straight Line (1877?) and his famous 'proof' of the Four Colour Theorem. FRS in 1881. Treasurer of the RS in 1898-1919. Kt in 1912.
- John Maynard Keynes, later Baron Keynes of Tilton (1883-1946) lived at 38 Brunswick street, c1911, and 3 Gower Street, c1915-1916. He then lived at 46 & 47 Gordon Square, 1916-1946 (Blue Plaque). He only used the drawing room of No. 47, renting out the rest. He became a Governor of the Bank of England. ; ;  In the 1970s, the UL Institute of Computer Science occupied these buildings.
- Dionysius Lardner ( -1859) came to London as Professor of Natural Philosophy at UCL and produced many popular works on science and edited the Cabinet Encyclopedia. His profits from these and his lecturing were enormous - he made £40,000 on a lecture tour to America - more than sufficient to pay off a trifling bill of £8000 for eloping with a Mrs. Heaviside, the wife of a cavalry officer. After returning from America, he settled in Paris. ; 
- William Laud (1573-1645) was a mathematician in his youth. He was Bishop of London from 1630 and Archbishop of Canterbury from 1633. He was imprisoned in the Tower and executed on Tower Hill nearby . See under Lambeth Palace.
- Derrick Henry Lehmer and Emma Lehmer were in Cambridge in 1938-1939, when D.H. had a Guggenheim Fellowship. They ran out of money and had to return to the USA early, which turned out to be fortunate as the ship they had originally intended to use never sailed due to the outbreak of war - the ship they left on was one of the last to cross the Atlantic.
- Angelo John Lewis, "Professor Louis Hoffmann" (1839-1919), was the leading writer on magic, games, amusements, puzzles, etc. at the end of the last century. He was born at 3 Crescent Place, Mornington Crescent and was called to the Chancery Bar in 1861 . In 1877, he was in Mornington Crescent . He lived at Ireton Lodge, Cromwell Ave., N. - presumably the Cromwell Ave. in Highgate . Another source says he retired to Hastings about 1903 and died in 1917.
- "Alice" Liddell was born at 19 Dean's Yard in 1852 while her father was headmaster of Westminster School. They moved to Oxford in 1855. She was married to Reginald Hargreaves in Westminster Abbey on 15 Sep 1880. She later lived in Lyndhurst, Hampshire, but was cremated at Golders Green Crematorium in 1934. .
- Kathleen Lonsdale (1903-1971) was a crystallographer at UCL and then Professor of Chemistry. One of the first woman FRSs in 1945. DBE, 1956. First woman PBAAS, 1967.
- Ada Byron, later Ada King, later Countess of Lovelace, (1815-1852), was born in Lord Byron's house, 13 Piccadilly Terrace (now 139 Piccadilly). Lady Byron abandoned Lord Byron shortly thereafter, taking Ada with her. Shortly after, Lady Byron (and presumably Ada) was at Branch Hill Lodge (also known as Bleak Hall or Judge's Bench House), several times rebuilt and now an old people's home in Branch Hill near West Heath Road, Hampstead. 
In 1833, Ada meets Babbage and later visits Dorset Street where she is fascinated by the Difference Engine.
After Ada's marriage to Lord King in 1835, (he was later Earl of Lovelace in 1838), they bought and rebuilt 10 (now 12) St James's Square. In 1840, Ada begins studying with Augustus De Morgan. In 1842-1843, she translated and annotated the famous Memoir on Babbage's Analytical Engine at St James's Square. The Lovelaces later lived at 6 (now 32, but the building has been replaced) Great Cumberland Place, Marble Arch, where she died in great agony, aggravated by her mother taking over the house, dismissing Ada's servants, terminating her pain-killing drugs and refusing to let Babbage and other friends see Ada. At her request, her husband had her buried beside her father at Newstead Abbey.  I recently examined the Great Cumberland Place site - it is now the Marble Arch Synagogue. Mrs Moore says it was razed to the ground and rebuilt sometime after the war, though this is not obvious from the outside.
 says that the Lovelaces lived at Sandown House, Esher, Surrey, from c1841 until her death. Her mother, Lady Byron, lived at nearby Moore Place from 1841 to 1852. (The Lovelaces had several country houses and I don't know which one(s) they used most - see under Ockham and Porlock for three other houses.)
Following on my suggestion, English Heritage erected a Blue Plaque on 12 St James's Square on 12 Oct 1992. John Barnes, Chairman of ADA UK and a major developer of ADA, unveiled the plaque. (I had proposed that a Blue Plaque be erected on 139 Piccadilly, but English Heritage felt that building has been too much changed to count.)
Ada's daughter Anne (1837-1917) married the colourful poet, diplomat, Arabist and womanizer, Wilfred Scawen Blunt (1840-1922). Lady Anne was also a traveller and Arabist. They established the Crabbett Park Arabian Stud at Worth, Sussex. They lived at 15 Buckingham Gate, SW1 (Blue Plaque). 
- Percy Alexander MacMahon (1854-1929) was a student at the Royal Military Academy in 1871-1873. After service in India, he returned as Instructor in Mathematics in 1882-1890, then Professor of Physics at the Ordnance College (where??) in 1890-1897. Retired from Army as Major, 1898. Deputy Warden of the Standards for the Board of Trade in 1904-1920 and served on the Comit Internationale des Poids et Mesures. A Secretary of the British Association in 1902-1914. Royal Medal, 1900, and Sylvester Medal, 1919, of the Royal Society. PLMS 1894-1896. Combinatory Analysis, 1915. PRAS, 1917. New Mathematical Pastimes, 1921. De Morgan Medal of LMS, 1928. Lived in Westminster, but in 1922 he retired to Cambridge.
- Thomas Robert Malthus (1766-1834) is known to have lived in a series of London garrets in the late 18C and early 19C. c1800, he used 57 Great Russell Street, the office and residence of his friend, the solicitor William Bray, as his official address. His 1798 Essay on the Principle of Population was apparently written in London. This book suggested the idea of 'survival of the fittest' to Darwin and Wallace. It was published anonymously, but his name appeared on the 2nd ed. of 1803. He left London by 1806, returning only for visits. 
- Karl Marx (1818-1883) wrote some papers on the foundations of calculus which are not profound but show a genuine interest in a real problem. He came to England in 1849 after 14 residences in three countries - I have not entered these! Lodged in Camberwell, Chelsea and Leicester Square, then lived at 64 Dean Street (demolished) for a few months before moving to the top floor of 28 Dean Street, Soho, in 1851-1856 (Blue Plaque) . Lived for a time at 9 Grafton Terrace, Kentish Town .  gives 46 Grafton Terrace. Lived at two addresses - 1, then 41 - both demolished, in Maitland Park Road, Chalk Farm, in 1864-1875 and 1875-1883 ; . The first was originally 1 Modena Villas and is now under the southern half of The Grange . His wife and he died at No. 41. This was demolished in the Second War, but there used to be a Blue Plaque at 41 Maitland Park Road. He used Seat G7 in the Reading Room of the British Museum.  He was buried in the unconsecrated part of Highgate Cemetery, with a monument greatly out of proportion to his mathematics ; . Several members of his family and some other revolutionaries are buried here.
- John Nevil Maskelyne (or Neville John) , descendent of the brother of the Astronomer Royal, was the best known magician in late 19C England and also a notable mechanic and inventor. He invented the coin lock as used in pay toilets, several proportionally spaced typewriters and he built numerous automata. His whist-playing 'Psycho' of 1875 should be in the London Museum, but I don't recall seeing it ; .  says it was seated on a glass cylinder so everyone could see it was not connected to anything, but the cylinder was hollow and the control was by air pressure!. There seem to have been two versions - the earlier could do arithmetic, but the later smoked a cigarette instead. The Maskelyne family presented it to the London Museum in 1934. The Director of the Museum recently told me that Psycho is not working. I have been told that a version has been restored to working order by a collector in Los Angeles.
- Nevil Maskelyne (or Neville) (1732-1811) was a student at Westminster School, then at Trinity College, Cambridge. About 1755, he was curate of Chipping Barnet, north of London. In 1761, he went to St Helena to observe the transit of Venus on 6 Jun. Although part of the transit was obscured by cloud, he demonstrated that the lunar distance method could determine longitude at sea and accurately determined the longitude of St Helena. On his return in May 1762, he published The British Mariner's Guide which was an English translation of Tobias Mayer's tables with instructions for their use. Astronomer Royal from 1765 to 1811. He resisted Harrison's chronometer as a solution to the longitude problem, preferring the astronomical method of lunar distances and frequently sabotaged the tests and even the chronometers in hopes of winning the Longitude Prize himself . He founded the Nautical Almanac in 1766. He determined , the universal gravitational constant in 1774-1776 - see also Schiehallion in Scotland.
- James Clerk Maxwell spent five years, 1860-1865, as Professor of Physics and Astronomy at Kings College London (Institute of Physics plaque in the courtyard). During that time, he lived at 16 Palace Gardens Terrace, Kensington, which has a Blue Plaque. FRS in 1861. While here, he produced "A memoir on colours" and the first colour photograph (both in 1861); "A dynamical theory of the electro-magnetic field" (1864) and "A dynamical theory of gases" (1866). He carried out many of the necessary experiments in his garret, including his experiments on the viscosity of gases, for which Mrs Maxwell acted as stoker and temperature regulator.  In 1861, he made the first colour photograph, which he exhibited to the Royal Institution on 17 May 1861. He photographed a tartan ribbon through red, blue and green filters, then projected the results through filters to get the recombined colours on a screen. The experiment should not have worked - his plates were not sensitive to red, but the red dye also reflected ultraviolet which the plate did record!  His 1864 paper included 'Maxwell's equations', but he had discovered the key fact that the ratio of the electromagnetic and electrostatic units was the speed of light by 19 Oct 1861 and the consequence that light and electromagnetism were the same when he communicated this to Faraday . This established that light was an electromagnetic wave, soon leading to wireless and radio, etc. He found the teaching load at KCL onerous and retired in 1865. In the Ball albums at Cambridge is a letter from Maxwell at 86 Hereford Road, Westbourne Grove, on 12 Apr 1869. Memorial floor inscription in Westminster Abbey, near Newton's grave.
- Sir Walter Mildmay (c1520-1589), was a successful financier who became Chancellor of the Exchequer under Edward VI and Elizabeth I. He founded Emmanuel College, Cambridge. He is buried in St Bartholomew's, Smithfield, London. 
- James Mill (1773-1836): see mainly the next entry. He was buried at St Mary Abbots Kensington and there is a memorial to him by the west door inside the church.
- John Stuart Mill (1806-1873) was born at 12 Rodney Terrace (now Rodney Road), Pentonville, and lived there until 1810. The house is gone. In 1810, they stayed briefly at one of Bentham's houses, where Milton had lived! In 1810-1814, they lived at Newington Green . In 1814-1831, his parents and he lived at what is now 40 Queen Anne's Gate, part of Jeremy Bentham's property - Bentham was in the adjacent house. He spent 1824-1858 as a civil servant in the East India Company, rising to a high position. In 1831-1836, his parents and he lived in a vanished villa in what is now Vicarage Gate, Kensington Church Street, where James Mill died in 1836. He then lived at 18 Kensington Square (Blue Plaque) in 1837-1851, where he wrote his System of Logic (1843) and Principles of Political Economy (with Harriet Taylor, 1848). ;  In 1851, after she had been widowed, Mill married his long-time friend and collaborator Harriet Taylor. He then bought a house in Blackheath Park (vanished). After her death in Avignon in 1858, he stayed there most of the rest of his life, but had a home at 10 Albert Mansions, Victoria Street, in 1871-1873 (vanished).  Statue on Victoria Embankment, east of Temple Station ; .
- Alan Alexander Milne did mathematics at Cambridge, but then went into journalism and writing. He lived at 13 Mallord Street, off Kings Road, SW3 (Blue Plaque), in 1920-1939. 
- Abraham De Moivre (1667-1754) was a Huguenot who came to England after the Revocation of the Edict of Nantes in 1687. FRS in 1697. Became the leading expert on Newton's Principia, to the extent that Newton referred questions to him. His Doctrine of Chances of 1718 greatly expanded the mathematical theory of probability which Bernoulli had started in 1713. He was a habitue of Slaughter's Coffee House, St Martin's Lane at Cranbourn St This was near SOHO which was a major area for Huguenot refugees. The Coffee House started in 1692 and was demolished in 1843. De Moivre was a kind of consulting mathematician there. This was a centre for chess players, including Abraham de Moivre (1667-1750), the mathematician who lived for nearly thirty years on the petty sums he made at Slaughter's by chess.  and François-André Philidor. De Moivre was buried at St Martin-in-the-Fields, Trafalgar Square, but the burials were shifted long ago.
- Samuel Molyneux (1689-1728) (son of the William Molyneux noted elsewhere) was Secretary to the Prince of Wales and an enthusiastic amateur astronomer. He erected a 24-foot zenith sector at his house, Kew House, Kew Green in 1725. He and Bradley (qv above) began making observations of GammaDraconis in the hopes of confirming a measurable parallax announced by Hooke.However, they discovered a displacement in the opposite direction. Bradley continued observations from Wanstead, leading to his discovery of the aberration of light in 1728. In 1831 or 1834, William IV had a sundial erected on the Kew Green site - Kew House was in what is now Kew Gardens and was demolished in 1804, but the sundial is now in front of the Dutch House in the Gardens. See THIS LINK
- Jonas Moore was made tutor to the Duke of York by Charles I. A friend of Pepys, who records : "Up, and to my chamber, whither Jonas Moore comes, ... and tells me the mighty use of Napier's bones" . FRS, 1674. Surveyor General of the Ordnance and Governor of the Tower of London, c1675. Instigator of the Royal Observatory, qv, and he even donated the instruments to Flamsteed because there were no funding for them. Flamsteed was his guest at the Tower for the year before he became Astronomer Royal. A founder of Christ's Hospital school - he wrote New Systeme of the Mathematics, with contributions from Flamsteed and Halley, for the school.
- L. J. Mordell relates that the fundamental idea for his work on the class-number of definite ternary quadratic forms occurred while he was walking down Oxford Street in May 1916 .
- Sir Samuel Morland (1625-1696), inventor of an adding machine, a multiplying machine and other mathematical instruments (cf entries for Science Museum, London and Cambridge), possibly including the barometer with a bent tube, is buried in St Paul's Church, Queen Caroline St, Hammersmith, west London. He was Master of Mechanics to Charles II, but died in poverty. His 1666 calculator, described in his The Description and Use of Two Arithmetick Instruments of 1673, may have been the first successful multiplying calculator. However, he also produced a simple adding machine at the same time and Pepys disparaged it: 'very pretty, but not very useful' . ; 
- Henry Moseley (1801-1872) came to London as first professor of Natural and Experimental Philosophy and Astronomy at KCL in 1831-1844. He was also Chaplain to the College in 1831-1833. He then became one of the first HM Inspectors of schools. Mechanical Principles of Engineering and Architecture, 1843, among other books. Perhaps his most significant work was a paper "On the dynamical stability and on the oscillations of floating bodies" in the Phil. Trans. of 1850, which established the formulae for calculating the dynamical stability of ships which were used for many years. He served as a juror at the Great Exhibition of 1851 and as Chaplain to the Queen from 1855. He seems to have lived in Wandsworth as he married a lady of Wandsworth Common in 1835 and their son, H. N. Moseley, the naturalist, was born in Wandsworth in 1844.
- Joseph Moxon (1627-1691) was well known as a printer, letter-cutter, typefounder, mathematician, hydrographer and maker of scientific instruments, globes, etc. who wrote, translated and published works of scientific and technical interest, being one of the principal printers of mathematical tables. Royal Hydrographer in 1662. His Mechanick Exercises, or the doctrine of handy-works, in 14 parts, 1677-1680, was the first technical encyclopedia, revealing many techniques that were previously guild secrets. It has been described as the reason why England was the home of the industrial revolution and the source of all do-it-yourself books. It was also notable as the first English book issued in parts. Moxon was a friend of Hooke. FRS in 1678. In 1683-1684, he produced Mechanick Exercises on the Whole Art of Printing, the first printer's manual in English. He translated and published Georg Mohr's 1672 book which showed any geometric construction can be done with compass alone.