If you get lucky and buy a piece by Mr Upandcoming, hold on to it for a decade or two and then sell on an upswing of popularity, you can make millions.

Worse, if your surname is Saatchi, you can define the market and use it create millions by talking up artists you happen to collect.

(Until a lot of your collection disappears in a mysterious and unexpected fire. Allegedly.)

This game is played more often than you might expect.