In February 1861 a 21-year-old French medievalist called Paul Meyer walked into Sotheby’s auction house near Covent Garden. He had been sent by the Bibliothèque Imperiale to bid on their behalf at the sale of the Savile collection of rare manuscripts, and though he did not have the funds to compete with the big players at the auction, he did at least manage to see, before it disappeared for the next 20 years into the insatiable collector’s maw of Sir Thomas Phillipps, a rhymed verse chronicle of 19,000-odd lines in Norman French that was to become the great obsession of...