Agatha Christie

Agatha Christie was a famous Human writer in the 20th century. Christie was best known as a writer of murder mysteries. Her prolific body of work was in print billions of years after her death, establishing her as the best-selling author of all time.

Life
Before they met, the Doctor had declared to Martha Jones that he wanted to meet her. (DW: Last of the Time Lords.

In 1926, having found out that her husband had begun an extramarital affair, Agatha Christie nevertheless attended a party and met the Doctor and Donna Noble. Together, she assisted them in defeating a confused Vespiform after he committed a series of murders under the influence of Christie's own The Murder of Roger Ackroyd. During this adventure, Donna accidentally created minor anachronisms by making references to Christie's not-yet-written Murder on the Orient Express and her not-yet-created character of Miss Marple. After defeating the Vespifom, a psychic link she had formed with the creature resulted in her losing consciousness.

The Doctor, surmising that this event is what caused her memory loss and unexplained absence, actually contributed to this historical event by taking the unconscious Christie forward eleven days and leaving her outside a hotel in Harrogate where she revived with no conscious memory of the events. Christie was later known for her mysterious disappearance in which her car was found abandoned and had crashed into a tree by the side of a lake. Fragments of memory later emerged in her storytelling including Donna's suggestions, as well as the Vespiform's wasp-like appearance, which inspired a plot element in her later book, Death in the Clouds. (DW: The Unicorn and the Wasp).

Works
Apart from The Murder of Roger Ackryod, Christie had written five other novels by 1926. She had not yet written Murder on the Orient Express. A subconscious memory of the Vespiform remained with Christie, so a wasp played a role in one of her subsequent novels, Death in the Clouds (DW: The Unicorn and the Wasp). Centuries after its publication, a copy of Murder on the Orient Express found its way into the possession of Professor Lasky (DW: Terror of the Vervoids).

Christie's works were still in print as late as the year 5,000,000,000, including Death in the Clouds (DW: The Unicorn and the Wasp).

Minor references and mentions

 * The Doctor had a signed first edition printing of The Murder of Roger Ackroyd which was missing the last page, leaving him to believe he would never find out who did it. (BFA: Storm Warning) Perhaps not coincidentally, of Christie's novels, only this fooled the Doctor as to the identity of the murderer. (DW: The Unicorn and the Wasp'')
 * He also once claimed Christie had travelled with him (BFA: Terror Firma).
 * This obviously contradicts the Doctor, in a later incarnation saying he wanted to meet her. (DW: Last of the Time Lords)

Influence
The murder mysteries of Agatha Christie had possibly already inspired the Doctor Who television story The Robots of Death, the Big Finish Productions audio play The Chimes of Midnight and, arguably, another television story, Horror of Fang Rock.

Appearance
With the exception of Elizabeth II, who has only appeared in cameos, the appearance of Agatha Christie as a character in The Unicorn and the Wasp marks the first time a "historical figure" of a person alive during the original 1963-89 run of Doctor Who, has appeared in the series. Her appearance as a character happened with the permission of her estate.

Historical accuracy
The Unicorn and the Wasp pretty clearly does not happen in early December. In reality, Agatha Christie vanished during that time of year. Additionally, "Agatha Christie" only used that name as a pen name, a fact not mentioned or dealt with in the story.

Deleted scene
In a scene included in the Series 4 DVD, late in her life, soon before her death, Christie begins to experience dreams and flashbacks related to her adventure with the Doctor. Ultimately, the Doctor and Donna visit her, at which point her memories of the adventure began to return; the Doctor proceeded to remind her of what happened. This scene does not present a continuity issue, as Donna is seen to be basically parroting the words the Doctor said to her (regarding Agatha being the best-selling writer of all time) in the original ending, allowing both to exist. The fact the Doctor has chosen to inform Agatha about the future edition of her book as well as remind her about what happened suggest the meeting takes place soon before her death, which would place the scene as taking place in 1976.