I wish I'd been more aware of Peter Landin a long time ago. Yes, I'd heard of his work a while back, but I simply didn't understand just how influential he'd been.
He was clearly influenced by John McCarthy's work on lisp as can be seen by his definition of the SECD machine. But there was so much more to him than that.
Tony Hoare credits Landin as one of the instructors who taught him Algol 60, particularly recursion, and thus allowed the elegant expression of QUICKSORT which Hoare has stated was his early claim to fame.
As a student, we heard about a language that Landin had created called ISWIM, which stood for If you See What I Mean. As a student we joked that what we really needed was DWIM or Do What I Mean.
He certainly had a sense of humor which comes out reading any of his papers or even their titles (see The next 700 programming languages as an example.
Landin was an early pioneer and would have been well worth knowing. I feel I should say more, about this remarkable man, but that's all I've got for now.