Given how much emotion was generated by the solution of a game that has always been seen as chess’s less serious cousin, one can only imagine the response when chess finally falls. Luckily for Schaeffer’s mailbag, he is unlikely to be around to see that. “We are certainly not going to solve chess in my lifetime,” he says. “It will need a real change in technology.”

We are used to exponential improvement in computing. After all, in two decades the hardest game solved by a computer increased in complexity by 100m. So why is Schaeffer pessimistic about chess?

Five hundred billion billion is big. But the number of atoms in the Earth is unimaginably big. The number of atoms in the universe is an unimaginably big number times an unimaginably big number. Chess is so complex that no one is certain how complex it is – estimates range between these two numbers.

“Very simply expressed, the problem of playing a perfect chess game is that there are too many possible chess games,” says David Levy, president of the International Computer Games Association – a body that, despite its title, has very little to do with Grand Theft Auto – and a lot to do with chess and draughts. “Remember, the pieces are not all the same. In checkers there are two pieces – the man and the king. In chess there are six pieces. That is a huge difference. The game of checkers – I don’t want to use the word ‘simple’ – but it is simple enough.”