The Doctor (The Cabinet of Light)

An incarnation of the Doctor helped Honoré Lechasseur defeat Mestizer.

Biography
The Doctor regenerated after being shot in the back shortly after meeting Mestizer at the bay in London. He spent several months lying low while Honoré Lechasseur conducted his investigations for him. (PROSE: The Cabinet of Light)

Working to defeat the Sodality, who had altered history in the 16th century, the Doctor learned of its workings, and how the High Executioner came to join the organisation.

Under the alias of Dr Smith, he arrived at the Sodality's headquarters in Buckingham Palace in 2586. He offered to help them hunt down all time sensitives and time channellers so that the creatures they were trying to summon would not destroy the human race. When the High Executioner refused to help him, she had him imprisoned so that he could not meddle any further. While being questioned by the High Executioner, he tried to convince her to abandon her plans to summon Mastho and turn on a different path, believing that she was the same good person she was before joining the Sodality. The Grand Master stopped their conversation, concerned that Dr Smith might be getting through to her.

The High Executioner returned to him of her own volition, intrigued by his words before. Smith asked her whether she would stop the Sodality and put history back on course if she had the choice. When she said yes, Smith left in his TARDIS, saying that he would soon show her that what he spoke of was possible.

He returned to the High Executioner at the moment she and the Sodality summoned Mastho. When the Daemon became enraged that the Child of Time Maria disobeyed him, the High Executioner was hit on the side of the head by him. Smith picked her unconscious form up and took her to his TARDIS. The Doctor dropped off the High Executioner in 1949, where she called herself by her real name, Emily Blandish, and would help the Doctor defeat Mestizer in his relative past. (PROSE: Child of Time)

Personality
The Doctor smoked cigarettes to improve his singing voice, (PROSE: The Cabinet of Light) though he also claimed that his body craved them. (PROSE: Child of Time) He had recently lost a travelling companion, which made him reluctant to take on a new one. (PROSE: The Cabinet of Light) He told the High Executioner that killing all the time sensitives and time channellers was a lesser evil than having Daemons kill the entire human race because of their existence, but later admitted that it was a lie to get their attention. He hadn't the patience for espionage and preferred to "charge on in". (PROSE: Child of Time)

Appearance
The Doctor wore a black coat with green collar, white shirt, a loose collar on the coat, exposing his neck and pronounced throat. He wore a hat and muffler. He was clean shaven on only his chin and lip. (PROSE: The Cabinet of Light) He had a domed head with black (PROSE: Child of Time) or brown hair which was receding. He was thin and gangly, (PROSE: Child of Time) but not too tall and had large hands. (PROSE: The Cabinet of Light) He was also known to wear a plum-coloured velvet smoking jacket and formal black trousers. (PROSE: Child of Time)

Behind the scenes

 * There is a marked similarity between the Shalka Doctor and this incarnation of the Doctor (from the thin frame, to the green clothing, to the receding black hair, and even to an ongoing effort to improve his singing voice). However such a similarity is entirely coincidental, as author Daniel O'Mahony worked on this story with no information that a new incarnation of the Doctor would be introduced just months after the publication of his novella.
 * In AHistory, Lance Parkin considers that this incarnation of the Doctor could be a result of the Sodality's alternate future and not actually have been from the "main" timeline.