Let’s imagine that you have, in your family, a pretty landscape that everyone thinks is by Signac. Or a Warhol silkscreen that your father bought from a friend in the days when they cost peanuts. Or that the squiggly painting you picked up at a car boot sale could, just possibly, be a Jackson Pollock.

All that is needed is get it authenticated and your artwork could be worth, literally, a fortune – in the case of the Pollock, a cool £25m. And the Signac and the Warhol could sell for six figures. But if they are fakes or copies, they would be virtually worthless.