James Watson

James Watson was a scientist who won the Nobel Prize in 1962 for his discoveries about DNA along with two other scientists, Crick and Wilkins. (PROSE: The Taint) According to one source, these discoveries were also made with the help of Rosalind Franklin. (PROSE: Time Traveller's Diary)

Watson was an old friend of the Doctor. In 1968, the Second Doctor visited Watson in London and got Watson to sign a copy of his latest book for his companion Zoe Heriot. (PROSE: The Avant Guardian) Like Watson, Zoe was a scientist and specialised in astrophysics. (TV: The Wheel in Space)

Behind the scenes
The Avant Guardian does not mention the title of the book that the Doctor had Watson sign for Zoe, but in the real world, Watson's most recent book as of 1968 was, published the same year. The Double Helix is an autobiographical book about his discoveries concerning the structure of DNA.