[...] Aladdin’s cave of treasures, trophies and discoveries awaits all who travel to Maastricht in the Netherlands over the next two weeks for The European Fine Art Fair (Tefaf). It is that sense of impending discovery that explains why this is one of the fairs best attended by museum directors and wealthy private collectors, from Dutch burghers and Middle Eastern sheikhs to American philanthropists looking to endow a museum with something special.

Tefaf is a place for dealers to upstage the salerooms, particularly by demonstrating their superior knowledge and wisdom; they are constantly outsmarting the auction rooms. Last year, Old Master dealer and Rubens specialist Fergus Hall spotted a red chalk drawing of a putto or cherub on the website of a small auction room in Dorset catalogued as “Dutch School” and with an estimate of £1,000. “I had a confident hunch that it was a Rubens,” says Hall.

Someone else also had a hunch, but it was not as confident as Hall’s, and Hall ended up paying £23,000 for it. He then showed the drawing to several Rubens experts, including Christopher Brown at the Ashmolean, Jane Turner at the Rijksmuseum, and David Jaffe at the National Gallery, and all concurred that it was a study from circa 1618 for a Rubens painting of the Virgin and Child surrounded by the Holy Innocents in the Louvre Museum. Only very few such studies have survived, says Hall, who is now asking £150,000 for it.