The Einstein of maths

The odds are that the name Alexandre Grothendieck will mean little or nothing to most Spectator readers. It’s a name I heard for the first time in high summer two years or so ago, not long, as I remember it, after the film A Beautiful Mind had come out. I was in the garden of my friend Umar’s house in Cambridge, and we were waiting for his ancient cast-iron barbecue, Camp Freddie, to cook some sausages.

Umar is a mathematician of considerable braininess, and when we are together we often end up talking maths. That is, I tend to ask him to explain what he does, and he tends to try, and I tend not to understand. But sometimes we strike gold. An entire afternoon was once passed happily playing logic games involving prisoners with different-coloured hats. I have giggled ignorantly at maths jokes (‘What’s purple and commutes?’ ‘An Abelian grape’), hummed and hawed over the question of whether maths is discovered or invented, and been mindboggled for a week after he explained the concept of the ‘cardinality of infinities’ (some infinities are bigger than others, it turns out).