Every year 10 billion dollars’ worth of art is stolen around the world, making art theft the third most lucrative illegal activity on our planet, after drugs and weapons. But, when it comes to establishing who the real art thieves are, the picture is far from clear. With paintings sometimes ‘stolen to order’ by drug gangs and arms dealers, using the works to launder money, these top three illegal activities have become increasingly intertwined.

Although museums aren’t generally flush with cash, the biggest and best funded have responded to the threat of art theft by spending millions on high-tech security – think of one of the particularly elaborate episodes in ‘Mission Impossible’! But, as the sophistication of security systems has increased, so have the strategies of professional thieves, who have often flummoxed the art world, for example thieves walked into Stockholm’s National Museum in 2000 (during opening hours!) and swiped two Renoirs and a Rembrandt, with apparent ease.

But the thieves aren’t the only ones who stand to make money in the murky world of art crime: the forgers can also make a tidy profit. In fact, experts estimate that 40% of art is fake.

As long as art has been produced, it has been copied - the ancient Romans made reproductions of Greek art by the chariot-load, then the Europeans copied the Romans and so on.

Before the 19th century, copying the work of other artists was considered a respectable form of homage to the old masters and an important part of an artist’s training. It was only when art became a commercial commodity, and the demand for fine art exceeded the supply, that the misuse of signatures became rampant. Controlling legislation was introduced and the formerly respected tradition of copying art became forgery.