Inmos’ Occam-based verification of their FPU in collaboration with researchers at Bristol and Oxford iirc? Citation: http://people.cs.bris.ac.uk/~dave/formalmethods.pdf
David May was my PhD supervisor and always spoke very highly of Sir Tony Hoare.
Edit: I’m also lucky enough to have worked with Geoff Barrett, the guy that completed that formal verification (and went on to do numerous other interesting things). Some people may be interested to learn that this work was the very first formal verification of an FPU - and the famous Intel FPU bug could have been avoided had Intel been using the verification methods that the Inmos and University teams pioneered.
I actually had two PhD advisors [1]; Jim Woodcock and Simon Foster.
Both of them are legitimately wonderful and intelligent humans that I can only use positive adjectives to describe, but the one I was referring to in this was Jim Woodcock [2]. He had many, many nice things to say about Tony Hoare.
[1] Just so I'm not misleading people, I didn't finish my PhD. No fault at all of the advisor or the school.
[2] https://en.wikipedia.org/wiki/Jim_Woodcock
I remember Jim Woodcock as really inspirational - he was working with my PhD supervisor in 1987. We were working on a variant of Z for specifying what, today, we would call CRDTs. I was also lucky enough to meet Tony Hoare the same year and discuss those concepts.