Spotted high up on a wall at Sotheby’s last year, the painting of a shipwreck and its survivors was attributed to “the Studio of Claude-Joseph Vernet”, a French artist who catered for the 18th-century romantic taste for the “terrible” and the picturesque. Although signed, it was thought not to be by Vernet, but by one of his studio assistants. Consequently, it was knocked down to London dealer Theo Johns, for just £25,000.

Since then, Johns has had the painting cleaned to reveal one of Vernet’s trademark lighthouses perched on a cliff (pictured above), which, for some unknown reason, had been painted over in the 20th century. Johns then tracked the painting’s exhibition history and found it had been included in the 1926 catalogue raisonne of the artist’s work. It is now on offer for £400,000, which is par for the course for a large, early shipwreck scene by Vernet, an artist who is represented in museums the world over.