Since art auctions were invented, they have served to hype artists’ prices. It can happen during an artist’s lifetime — Jeff Koons’s ‘Balloon Dog’ — or half a millennium after their death — Leonardo’s ‘Salvator Mundi’. And it can sometimes restore a lost reputation, as happened with Frans Hals.

When the picture now famous as ‘The Laughing Cavalier’ came up for auction in Paris in 1865, Hals was all but forgotten.