Xenocrates was an individual whose biography was kept at the York Central Library.
The Ninth Doctor defaced a copy of his biography with a "hand-held electronic 'eraser' device" prior to March 2005, along with the biographies of HG Wells, Boudica, Tancred Norman, Blaise Pascal and Margaret Thatcher. Senior librarian Ms Millicent Davies banned the Doctor from the York Central Library and then applied to get the Doctor an ASBO to ban him from all UK libraries. (PROSE: Have You Seen This Man?)