One of Callow's best-known books is "Love Is Where It Falls", an analysis of his 11-year relationship with Peggy Ramsay (1908–91), a prominent British theatrical agent from the 1960s to the 1980s. He has also written extensively about Charles Dickens, whom he has played several times: in a one-man show, "The Mystery of Charles Dickens" by Peter Ackroyd; in the films "", and ";" and on television several times including "An Audience with Charles Dickens" (BBC, 1996) and in "The Unquiet Dead", a 2005 episode of the BBC science-fiction series "Doctor Who". He returned to "Doctor Who" for the 2011 season finale, again taking the role of Dickens.