The sketch came to light after the owner found it in a wardrobe and contacted Christie's. Even from initial photographs, their experts were sure it was by the 17th-century Dutch master.

"We always dream of finding new drawings by the great artists, but it happens very rarely nowadays," said Benjamin Peronnet, head of old master drawings at Christie's. "That made this discovery all the more exciting."

A Blind Beggar With a Boy and a Dog is a black chalk study measuring 13cm by 8.5cm (about 5in by 3.3in). It does not relate to a known painting but the composition is echoed in a drawing in the Kupferstichkabinett, the vast prints and drawings collection in Berlin's state museum.

Peronnet said: "When we began our research, we were surprised to find an almost identical drawing of a beggar in Berlin – it usually isn't good news when you find … a similar drawing in a museum, because it can mean that the [discovery] … is only a copy."