Tony Hoare (1934-2026)

Turing Award winner and former Oxford professor Tony Hoare passed away last Thursday at the age of 92. Hoare is famous for quicksort, ALGOL, Hoare logic and so much more. Jim Miles gives his personal reflections.

Jill Hoare, Tony Hoare, Jim Miles. Cambridge, 7 September 2021

Last Thursday (5th March 2026), Tony Hoare passed away, at the age of 92. He made many important contributions to Computer Science, which go well beyond just the one for which most Maths/CompSci undergraduates might know his name: the quicksort algorithm. His achievements in the field are covered comprehensively across easy-to-find books and articles, and I am sure will be addressed in detail as obituaries are published over the coming weeks. I was invited in this entry to remember the Tony that I knew, so here I will be writing about his personality from the occasions that I met him.

I visited Tony Hoare several times in the past 5 years, as we both live in Cambridge (UK) and it turned out that my family knew his. As a Mathematics graduate, I was very keen to meet and learn about his life from the great man himself. I was further prompted by a post on this blog which mentioned Tony a few times and summarised a relevant portion of his work. I took a print out of that entry the first time I visited him to help break the ice - it is the green sheet of paper in the picture above.

Tony read the entry and smiled, clearly recalling very well the material of his that it referenced, and then elaborating a bit, explaining how vastly programs had scaled up in a rather short space of time and how they typically require different methods than many of those he had been developing in the early days.

I was aware that Tony had studied Classics and Philosophy at university so I was keen to learn how one thing had led to another in the development of his career. He explained that after completing his degree he had been intensively trained in Russian on the Joint Services School for Linguists programme and was also personally very interested in statistics as well as the emerging and exciting world of computers. This meant that after his National Service (which was essentially the JSSL) he took on a job 'demonstrating' a type of early computer, in particular globally, and especially in the Soviet Union. He described the place of these demonstrations as 'fairs' but I suppose we might now call them 'expos'. In a sense, this seemed like a very modest description of his job, when in fact - reading up on Tony's career - he was also involved in the development of code for these devices, but perhaps that's a historical quirk of the period: being a demonstrator of these machines meant really knowing them inside and out to the point of acting on the dev team (AND, one might deduce, being fluent in Russian!).

Tony would tell these stories with a clarity and warmth that made it clear that certainly he was still entirely 'all there' mentally, and that his memory was pinpoint sharp, even if there were some physical health issues, typical for anyone who makes it so far into their 80s (and, as we now know, beyond!).

A story that I was determined to hear from the source was the legendary quicksort 'wager'. The story goes that Tony told his boss at Elliott Brothers Ltd that he knew a faster sorting algorithm than the one that he had just implemented for the company. He was told 'I bet you sixpence you don't!'. Lo and behold, quicksort WAS faster. I asked Tony to tell this story pretty much every time we met, because I enjoyed it so much and it always put a smile on both of our faces. To his credit, Tony never tired of telling me this story 'right from the top'. I had hoped to visit again in the past year and record him telling it so that there was a record, but unfortunately this did not happen. However, I discover that it is indeed recorded elsewhere. One detail I might be able to add is that I asked Tony if indeed the wager was paid out or if it had merely been a figure of speech. He confirmed that indeed he WAS paid the wager (!). A detail of this story that I find particularly reflective of Tony's humble personality is that he went ahead and implemented the slower algorithm he was asked to, while he believed quicksort to be faster, and before chiming in with this belief. It speaks to a professionalism that Tony always carried.

About 50% of our meetings were spent talking about these matters relating to his career, while the rest varied across a vast range of topics. In particular, I wanted to ask him about a story that I had heard from a relative, that Tony - whilst working at Microsoft in Cambridge - would like to slip out some afternoons and watch films at the local Arts Picturehouse. This had come about because on one occasion a current film in question was brought up in conversation and it transpired Tony had seen it, much to the bemusement of some present. The jig was up - Tony admitted that, yes, sometimes he would nip out on an afternoon and visit the cinema. When I met Tony and gently questioned him on this anecdote he confirmed that indeed this was one of his pleasures and his position at Microsoft more than accommodated it.

On the topic of films, I wanted to follow up with Tony a quote that I have seen online attributed to him about Hollywood portrayal of geniuses, often especially in relation to Good Will Hunting. A typical example is: "Hollywood's idea of genius is Good Will Hunting: someone who can solve any problem instantly. In reality, geniuses struggle with a single problem for years". Tony agreed with the idea that cinema often misrepresents how ability in abstract fields such as mathematics is learned over countless hours of thought, rather than - as the movies like to make out - imparted, unexplained, to people of 'genius'. However, he was unsure where exactly he had said this or how/why it had gotten onto the internet, and he agreed that online quotes on the subject, attributed to him, may well be erroneous.

One final note I would like to share from these meetings with Tony is perhaps the most intriguing of what he said, but also the one he delivered with the greatest outright confidence. In a discussion about the developments of computers in the future - whether we are reaching limits of Moore's Law, whether Quantum Computers will be required to reinvigorate progress, and other rather shallow and obvious hardware talking points raised by me in an effort to spark Tony's interest - he said 'Well, of course, nothing we have even comes close to what the government has access to. They will always be years ahead of what you can imagine'. When pressed on this, in particular whether he believed such technology to be on the scale of solving the large prime factorisation that the world's cryptographic protocols are based on, he was cagey and shrugged enigmatically. One wonders what he had seen, or perhaps he was engaging in a bit of knowing trolling; Tony had a fantastic sense of humour and was certainly capable of leading me down the garden path with irony and satire before I realised a joke was being made.

I will greatly miss this humour, patience, and sharpness of mind, as I miss everything else about Tony.

RIP Tony Hoare (11 January 1934 - 5 March 2026)