Bill Gates calls him "the best person I know at predicting the future of artificial intelligence". He's received 19 honorary doctorates, and he's been widely recognised as a genius. But he's the sort of genius, it turns out, who's not very good at boiling a kettle. He offers me a cup of coffee and when I accept he heads into the kitchen to make it, filling a kettle with water, putting a teaspoon of instant coffee into a cup, and then moments later, pouring the unboiled water on top of it. He stirs the undissolving lumps and I wonder whether to say anything but instead let him add almond milk – not eating dairy is just one of his multiple dietary rules – and politely say thank you as he hands it to me. It is, by quite some way, the worst cup of coffee I have ever tasted.

But then, he has other things on his mind.