A trademark Vernet lighthouse is rediscovered London's auction rooms are revving up for their next contemporary art sales, timed to coincide with the Frieze art fair in October. Last week, Sotheby's announced its main lot was to be a Gerhard Richter abstract painting from the collection of rock star Eric Clapton. Clapton bought it in New York in 2001 for what was then a record £2.1 million. It returns to the rostrum with an estimate of £9 million. This week, Christie's will announce its main lot is a rare self-portrait by the eccentric German artist Martin Kippenberger (pictured), which carries the highest estimate yet for the artist at £2.5 million to £3.5 million. Kippenberger died in 1997 aged only 44, and was featured in a retrospective exhibition at Tate Modern in 2006, where this painting, which belongs to an old friend of the artist, was included. Now something of a cult figure, his works are handled by major galleries including Gagosian and Hauser & Wirth, and his prices on the private market have reached as much as £4 million or £5 million. An 18th-century painting that has rocketed in value since it was cleaned and the identity of the artist confirmed, will be a star exhibit at the Lapada (London and Provinicial Art & Antiques Dealers Association) fair, which opens in Berkeley Square today. 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. The pair of Wilton rugs signed by Francis Bacon, which were previewed on this page two weeks ago, have for the second time been withdrawn from auction, this time by Anderson & Garland in Newcastle. There were serious doubts raised by a specialist rug dealer in the Telegraph's online comment section whether the rugs were by Bacon, and the auctioneers, which had left any attribution open to opinion, are not now making any further statements on the matter. They were, however, rewarded with a record £280,000 for a 1922 art deco vase by René Lalique, bought by an American collector, far above the £20,000 estimate. The price is thought to be the highest ever for a work of art at auction in the North East of England.