A Francis Bacon painting is estimated to fetch at least 25 million pounds ($49 million) in a Feb. 6 sale, the most expensive artwork ever offered at a London auction, Christie's International said. The artist's "Triptych 1974-77" of figures on a beach is being sold in an evening sale, the auction house said in an e- mailed statement released today. "The market for Francis Bacon has been transformed in the last five years," said Pilar Ordovas, head of contemporary art at Christie's, London. "He now has a worldwide collector base. His iconography appeals to everybody." London's February sales will be the Western art market's next test after an 11-year quadrupling in the prices for top contemporary works. The record for Bacon, who died in 1992, was set in May, when Sotheby's sold one of his pope pictures, "Study for Innocent X," for $52.7 million in New York. The triptych's minimum estimate tops the 25 million-pound top figure that Sotheby's last week put on its 1969 single canvas Bacon, "Study of a Nude With Figure in a Mirror," which it will offer on Feb. 27 in a new standalone "contemporary week."The highest price so far achieved for any artwork at a London auction is the 49.5 million pounds that the late collector Kenneth Thomson paid at Sotheby's in July 2002 for Rubens's "Massacre of the Innocents." The estimate was 6 million pounds to 8 million pounds. Like Sotheby's, Christie's said its February auctions in London would carry the largest estimates ever. It estimates its sale of modern and Impressionist art on Feb. 4 will raise between 89 million pounds and 125 million pounds, and the contemporary auction two nights later will fetch 69 million pounds to 97 million pounds. Fewer Guarantees "We've been a bit more cautious about guarantees, a bit tighter in our editing this season," said Olivier Camu, head of Impressionist and modern art at Christie's London."Just nine works have been guaranteed, and these have a value of less than 10 million." Camu said the view of guarantees changed after the failure of Van Gogh's guaranteed "The Fields (Wheat Fields)",which failed to sell at Sotheby's New York on November, 2007, against an estimate of between $28 million and $35 million. Over the next three days, Sotheby's stock plunged 35 per cent. "That sale rang a bell," said Camu. "It showed there's a limit to how far sellers can push." Swiss Picasso The most expensive lot in the Christie's Impressionist and modern sale is a 1969 Picasso,"Homme Assis au Fusil"(Man Seated With Rifle), estimated at 5 million to 7 million pounds. The painting, entered by a private Swiss collector, has never been offered at auction before and isn't guaranteed, said Christie's. Nine lots by Kees van Dongen, Alexej von Jawlensky and other early-20th-century masters bought by the late Maurice Wohl, a U.K. office developer, are estimated at 8.3 million pounds. Eight drawings by the Austrian Expressionist Egon Schiele, sold to benefit the Neue Galerie in New York, are valued at 7.6 million pounds. According to Christie's, neither group is guaranteed. "We're going to see some solid prices for material that's fresh to the market and in good condition," said Richard Nagy, a London art dealer. "People are still buying." Ordovas said Christie's Feb. 6 auction was "set to break the record for any contemporary sale held in Europe." At 55 works, it is about half the size of the 101-lot sale at Christie's in June, which fetched the previous record of 74 million pounds with fees. "That sale was too long," said Ordovas. "People were getting tired at the end. We wanted to keep our February sale tight and concentrate on the highest quality." Beach Bathers Large-scale works by Gerhard Richter and Lucio Fontana will also be offered by Christie's at record estimate levels. Richter's guaranteed 1966 "Zwei Liebespaare" picture of beach bathers is valued at about 6 million pounds, and Fontana's 1965 "Concetto Spaziale, Attesa" is estimated at as much as 5.5 million pounds. Both estimates are higher than the artist's existing auction records, according to the saleroom result tracker Artnet. Ordovas said sellers were not deterred from entering high- value works in a sale to be held three weeks earlier than at Sotheby's and Phillips de Pury. "If anything, some collectors were making a positive choice to consign with us," said Ordovas. "Owners of classic contemporary works are aware of the crossover appeal to Impressionist and modern collectors."