In 1968 I sat his fourth-year undergraduate course in Lebesgue Measure and Integration in $\mathbb{R}^{n}$. His lecture notes, which he seemed to reproduce on the blackboard verbatim, were complete and appeared hand-written. I thought at the time that he must be planning to write a textbook. But, as far as I know, he never followed up. Years later, when I taught the same subject matter, I realised that he had made clever use of ordinate sets rather than the more common simple function approach to measurability. This saved a lot of generalisation when moving from $\mathbb{R}^{1}$ to $\mathbb{R}^{n}$.

The following year I registered for David's graduate course called "Introduction to Summability Theory." At that time, summability theory was David's main research area. And he used classical, as opposed to functional analytic, techniques. This course was a scary experience for the four graduate students registered. For starters, the textbook was G H Hardy's classic book "Divergent Series," which is not the easiest read. Then, the students did all the lecturing and the audience consisted not only of David, but of all faculty, visiting faculty and post-docs in the summability research group at Western. Each student felt considerable angst before and during his or her turn at the blackboard.

My main area of research has been the summability theory of series and integrals, in the study of which I have used both classical and functional analysis. I have also considered problems in measure theory and probability theory, and have done some work in number theory and some on approximate subgradients and coderivatives.

My most recent work has been in collaboration with J M Borwein and latterly also with B A Mares Jr. on some remarkable properties of single- and many-variable sinc integrals, in particular their relationships to volumes of certain symmetric convex polyhedra. This research involved some subtle Fourier transform techniques. I also worked with W Kratz and U Stadtmüller on one-sided Tauberian theorems for methods of summability based on Dirichlet series - these methods include standard power series methods as special cases. There are various outstanding problems in both these research areas which I intend to tackle in the future.

David and Jon were long time collaborators, and produced a series of papers together in various areas during 2000-2020. Jon was a mathematical jack of all trades, while David's analytic methods were always relevant. Seven of David's ten most highly cited papers in Mathematical Reviews were co-authored with Jon. The most highly cited of all is a 1995 paper which computes sums related to the Riemann zeta function - this is analytic number theory, and analysis.

Two years of judging at Canada-Wide Science Fairs (Whitehorse 1995, North Bay 1996). Judge at the International Science and Engineering Fair in Hamilton (1995). Part of group escorting Team Canada to the International Science and Engineering Fair in Tucson (1996), Louisville (1997, 2002), Fort Worth (1998), Philadelphia (1999), Detroit (2000), and San Jóse (2001). Member of the Youth Science Foundation Scientific Advisory Committee which selected Team Canada for these International Science and Engineering Fair's and also for the ones in Cleveland (2003) and Portland (2004).

He made a presentation in December 1992 to the Standing Committee on Administration of Justice of the Ontario Legislature in support of a private member's bill to remove a clause from the Ontario Human Rights Code which allows for discrimination of those aged 65 or more. The bill (which he had prompted a local MPP to introduce) had second reading approval, but was allowed to die when the parliamentary session ended and never reintroduced.

In his later years David was increasingly devoted to Bessie and his family, delighting in watching his grandchildren and great-grandchildren grow.

David Borwein died peacefully in his sleep on 3 September 2021, at home. He was 97 years old, enjoyed good health all his life, and left this world with his sharp intellect and wit intact. He is survived by a tight-knit family and community who love him, above all his wife Bessie, and daughter Sarah, his nine grandchildren and five great-grandchildren.

[My father taught me] about the 'erkenntnis und praxis' of mathematics: that strange blend of arts and science, of austere Platonic edifice and fallible human creation. I learned of the quiet satisfactions of an intellectual life, but not of a life lived in a vacuum. I was taught to make yet one more revision to a paper and to savour the polish and finish it provided. And, finally, my overarching memory is of my father, at frequent parties arranged by my more outgoing mother, playing generously if not exuberantly the role of host. By mid-evening his eyes would slightly glaze and a stream of cocktail napkins would issue forth covered with formulae and expressions in his careful and concise italic script. I have been unusually privileged. I have worked intensively with both brother and father as equals and have known my father as an intellectual peer for more than a quarter century. In every sense he has been "the best teacher I ever had."