One day in 2007, as many of the world’s greatest mathematicians were assembled in a lecture room at Montreal’s Centre de Recherches Mathématiques, an odd Englishman in his fifties shambled up to the chalkboard. This was Simon Phillips Norton, and although a few of the older mathematicians in the audience had once known him, to the rest he was just the subject of extraordinary, if not necessarily accurate rumour: a genius of the first order, receiving the highest mark ever achieved in Cambridge’s mathematics finals. As a young man his research was spectacular, but then suddenly, in the 1980s, he had some sort of collapse from which he’d never recovered. There was mention of his living in a dark cellar in Cambridge; an obsession with train and bus timetables; and unseemly hygiene.

He didn’t face the audience when he reached the front, but poked around in the chalk box, until – after much throat-clearing – he found a piece that would do. Then still facing away he stumblingly spelled out three words on the board:

C-h-e-r-o-k-e-e

R-o-m-a-n-i-a-n