From TARDIS Index File, the free Doctor Who reference.
J.K. Rowling (nee Joanne Rowling, later Joanne Murray) (b. 1965) was the author of the very successful Harry Potter series of novels, publishing seven volumes between 1997 and 2007. Her books were also adapted as a successful series of movies.
The Doctor and Martha Jones were fans of the Potter books, and the Doctor admitted to crying after reading the seventh volume. Later, when Potter's spell "expelliarmus" was given life in order to help William Shakespeare defeat the Carrionites, the Doctor exclaimed, "Good old J.K.!" (DW: The Shakespeare Code)
There is a possibly apocryphal account suggesting Rowling (or a successor) wrote as many as four more Harry Potter novels, which were later obtained by the Doctor. (EDA: The Gallifrey Chronicles) If a true account, then it's unclear to which book the Doctor was actually referring to in his discussion with Martha.
Behind the Scenes
- In 2005 Russell T Davies asked Rowling to write for Doctor Who, she said she was "was amused by the suggestion but simply doesn't have the time." She was writing the sixth Harry Potter novel at the time. 
- In his 2008 autobiography, A Writer's Tale, Davies reveals that he considered basing the 2008 Christmas special around a guest appearance by Rowling.
- The reference in The Gallifrey Chronicles to there being 11 Harry Potter novels can be seen as an anachronism (written in 2005, two years before the publication of Harry Potter and the Deathly Hallows, the author may have been unaware Rowling only planned seven books). However, Rowling has herself made comments since the publication of The Deathly Hallows that she hasn't dismissed the possibility of writing another Potter novel in the future; perhaps in the Who universe she did. The reference to the last book in The Shakespeare Code does not settle the issue, as the book is never actually referred to by name, so the Doctor could just as easily be referring to Book 11.
- ↑ J.K. Rowling Turns Down 'Dr. Who'
- ↑ A Brief History of Time (Travel): Rose
- ↑ Doctor Who News Page - Davies Book Preview, accessed Sept. 18, 2008