A Jeff Koons sculpture will be the most valuable work by the artist offered at auction in Europe when it goes on sale at Christie's International in London next month, the auction house said today in an e-mailed statement.The chromium steel "Balloon Flower (Magenta)" is expected to fetch about 12 million pounds ($23.8 million) when it is offered on June 30, Christie's said.The work was made in 1995-1999 as part of the artist's "Celebration" series of high-tech sculptures inspired by childhood memories. Four other versions of "Balloon Flower'' exist in four different colors, said the auction house. The seller is Dallas-based collector Howard Rachofsky, who has been guaranteed a minimum price, said Christie's."It was an agonizing decision to sell this iconic work," Rachofsky said in a telephone interview. "But I just felt this was the right piece to sell at the moment in order to expand the collection in other areas."He said that he had bought the sculpture, which is 11 feet (3.4 meters) high, for an undisclosed price from a group headed by the London-based dealer Anthony d'Offay.Rachofsky, a former hedge fund manager, said that his main areas of collecting interest were now American Minimalism, Italian Arte Povera and German painting from the 1980s and 1990s.In 2005, Howard and Cindy Rachofsky donated their collection by bequest to the Dallas Museum of Art. He consulted Koons on the latest sale.　'New Nexus'"Jeff was enthusiastic about the idea of selling in London," Rachofsky said. "It is the new nexus of the art world."In November 2007, another sculpture from the "Celebration'' series, ``Hanging Heart (Magenta/Gold),'' sold at Sotheby's in New York for $23.6 million with fees, making Koons the world's most expensive living artist at auction.He remained so until May 14 when Lucian Freud's "Benefits Supervisor Sleeping'' sold for $33.6 million at Christie's in New York. According to the Art Newspaper, the Freud was bought by the Russian billionaire Roman Abramovich, who has a house in London.In April, http://www.artinfo.com reported that $80 million had been paid for a Koons stainless steel "Rabbit" sculpture, dating from 1986, in a $500 million private auction of the collection of the late Ileana and Michael Sonnabend."That price makes the `Balloon Flower' look a steal," said Pilar Ordovas, Christie's head of contemporary art in London. "Only a few years ago, we wouldn't have thought of selling a major Koons work in London, but now the global nature of the market has made the city a vibrant place to sell.""Balloon Flower (Magenta)" will be put on public display in St. James's Square from June 21-30. Christie's June 30 auction of contemporary art also includes works by Francis Bacon and Freud, valued at 10 million pounds each.(Scott Reyburn writes about the art market for Bloomberg News. Any opinions expressed are his own.)