Bill Tutte

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Unsung mathematical mastermind whose work breaking wartime German codes led to the world's first electronic computer

Professor William 'Bill' Tutte, who has died in Canada aged 84, made an unsurpassed contribution to the success of the British wartime assault on enemy codes and ciphers at Bletchley Park.

Since 1974, a stream of histories and memoirs -- and, more recently, faction and fiction for stage and screen, as well as books -- have encouraged the belief that Bletchley was all about Enigma. This German cipher machine, used by all three arms of the Wehrmacht, was certainly a prime concern for the teams of mathematicians, classicists, crossword fanatics and chess players who made such huge efforts to break into enemy signal traffic. Penetrating the toughest Enigma ciphers was crucial, for example, to victory in the Battle of the Atlantic against the U-boats, and with it the Allies' ability to invade north Africa, Italy and France.

Bletchley Park, an unprepossessing Victorian mansion strategically equidistant between Oxford, Cambridge and London, was the wartime headquarters of the government code and cipher school (GC & CS, now restyled GCHQ and based at Cheltenham). It employed 10,000 people at its wartime peak. Its targets were not only German but also Japanese and Italian ciphers, aspects of its work still almost unknown.

Nor was the attack on German signals confined to Enigma. There was also the Lorenz machine, based on teleprinter technology and used for top-secret, high-level traffic by the German general staff.

Broadly speaking, what the eccentric mathematical genius Alan Turing did for Enigma, Bill Tutte did for cracking the Lorenz cipher, codenamed "Fish" by the British. But he did not have the benefit of the kind of pioneering work done on Enigma before the war in Poland, where mathematicians succeeded in replicating the intricate cross-wiring within the machine and its notorious wheels. Working backwards from painfully deciphered intercepts, they made a working construct, which they handed on to the French when Poland fell; they, in turn, passed it on to the British when France fell.

Working from scratch, Tutte performed, with colleagues, a similar feat against Lorenz by deducing from signal traffic how it worked and how it was built -- without ever having seen the machine itself, still less got his hands on a plan or drawing of it.

Tutte's humble origins gave no clue to the numerical genius he began to display at an early age. The son of a gardener, he was born at Newmarket, Suffolk, where he went to local schools. At 18, he was a natural candidate for a place at Trinity College, Cambridge, where he studied chemistry from 1935, before moving on to postgraduate research.

Joining the Trinity Mathematical Society, he worked with a few colleagues on an old mathematical conundrum, how to divide a square into smaller squares of different sizes. Their answer, published in a paper in 1940, attracted the attention of the Cambridge intelligence mafia, and led to his tutor's suggestion that he should join the GC & CS in 1941.

Within months, Tutte had achieved a breakthrough, thanks to a security blunder by a German operator. Two different texts of the same lengthy message were inter cepted, the one an apparently corrected or tidied-up version of the other. But each had the same opening letters, the identifying "indicator" to the recipient, and the same "padding", or throwaway letters, routinely added to all messages to confuse eavesdroppers and cryptanalysts.

It was the differences between the two versions -- and unremitting, solitary hard labour -- that enabled Tutte, after four months, to postulate the internal workings of the machine.

The Lorenz was linked to a teleprinter, and used the 32-character teleprinter alphabet (letters plus punctuation marks) converted into patterns of punched holes on paper tape. Tutte worked out that the machine enciphered its texts through a dozen wheels, but, as the war contin ued, the Germans applied more and more sophistication to the process. This prompted the development by post office engineers, working with Bletchley, of the world's first electronic computer, the Colossus -- a vast machine with radio valves and a tiny fraction of the capacity of a modern laptop.

This breakthrough, speeding up the process of penetrating intercepts, was in place early enough to help enormously with deducing German dispositions and intentions prior to Operation Overlord, the Allied invasion of Normandy in June 1944.

After this unique intellectual feat and contribution to the war effort -- for which he received no public recognition (at least Turing got an OBE, though some of the few in the know thought he deserved an earldom) -- Tutte modestly returned to academic life and mathematical studies at Cambridge. After earning his doctorate, he moved to the University of Toronto, and, in 1962, transferred to the University of Waterloo, Ontario. He became a fellow of the Royal Society in both Britain and Canada, and finished his career as professor emeritus on retirement in 1982. He was also awarded the Order of Canada.

Soon after his wife Dorothea died in 1994, Tutte returned to his roots in Newmarket, but went back to Waterloo two years ago. He had no children.

William Thomas Tutte, mathematician and cryptographer, born May 14 1917; died May 2 2002

Dan van der Vat

May 10, 2002 © Guardian Newspapers Limited