The dispersal in 1812 of the library of John Ker, Duke of Roxburghe (1740–1804) was the bibliographical event of the decade and a key moment in 'bibliomania'. The huge collection contained illuminated medieval manuscripts, incunabula, fifteen books printed by Caxton, and all four Shakespeare folios. The sale, orchestrated by the bookseller and auctioneer Robert Harding Evans (1777–1857), at…