WHENEVER Adam Sisman thought he had captured the leviathan that is John le Carre, the great man would twist away, “with a flick of his tail.” Such are the perils of embarking on a biography of a former spy whose best-selling novels are full of duplicitous characters, while betrayals and lies run through his plots and a long life that has been every bit as thrilling as that of his fictional spymaster George Smiley.