LONDON—Britain is fighting to keep an important Rubens masterpiece from being sold abroad, the Times (London) reports. The 6th Viscount Hampden, the owner of The Apotheosis of King James I died earlier this month, but before his death he had entered into negotiations to sell the painting, which he had loaned anonymously to the National Gallery since 1981. Sir Hugh Leggatt, the former Museums and Galleries Commissioner, has called on the Prime Minister to save the work from being sold. "This painting must never leave these shores under any circumstances," Leggatt said. "It is vital to our nation as the most important painting in the land." He added that estimating the value of a painting of such importance is almost impossible, but Rubens's The Massacre of the Innocents sold at Sotheby's in London for £49.5 million ($97.6 million) in 2002. The National Gallery, which recently bought Raphael's Madonna of the Pinks for £35 million, preventing it from leaving the country for the J. Paul Getty Museum in Los Angeles, lacks the funds to buy The Apotheosis of King James I, but the Tate has announced efforts to buy it and has applied for a grant from the National Heritage Memorial Fund.