(Photograph) - Cambridge University has launched an appeal to support its purchase of the Macclesfield Newton Collection, a major archive of Sir Issac Newton's letters and papers, which has been valued by Sotheby's the auctioneers at Pounds 6.4 million. The Heritage Lottery Fund has pledged Pounds 4.8 million, leaving the University Library to foot a bill of Pounds 1.6 million. Patrick Zutshi, head of the University Library manuscripts and archives department, hopes that trustees and sponsors will help Cambridge to keep the papers in Britain. Newton was a student and a fellow at Trinity College, and became Lucasian professor in 1669, the chair Stephen Hawking now holds. The Macclesfield Collection contains almost 5m of material and covers many of Newton's central interests, such as gravity and calculus. Photograph by JACKY CHAPMAN