The Doctor Agents
Since the second world war, a variety of agents, several connected to UNIT, have used the name The Doctor. These agents have always been involved in incidents similar to those UNIT has tended to deal with. These agents follow a set pattern. Always male, they appear with one, or more, young assistants and then display advanced scientific knowledge and eccentricity, whilst being central to the resolution of an incident or a crisis.
With the exception of The UNIT Doctor who was UNIT's scientific advisor in the early 1970s, all of these Doctors have appeared just before an incident and disappeared without trace straight afterwards. We strongly suspect that The Doctor is a standard name for a particular series of agents used by Department C-19, as almost all of the agents had provable links to either UNIT or C-19.
Evidence suggests that C-19 had only one Doctor agent at a time, though occasionally, there is evidence of a successor or a backup agent. Each Doctor agent had a distinct face and persona, suggesting that replacement agents rather than plastic surgery were the cause of differing faces.
The problems with this approach come with the dates of the appearances. Although, generally, each agent fits into a particular time period, there are some major discrepancies. The Scottish Doctor, for example, was active between World War 2 and 1963 and again from the late 1980s, as well as turning up in 1976. However, all the descriptions of him from every incident estimate that he was in his 40's, and are consistent about his personality.
One explanation for this is that C-19 used plastic surgery and brainwashing to recreate this agent, rather than create a whole new one. Other discrepancies may well be agents brought out of retirement when the current agent was unavailable. As far as we are aware there have been seven faces of the Doctor, each with it's own distinct personality and specialities.
I have assigned arbitrary names to each one in this website in order to distinguish between them. What follows from the links below is a brief description of each one's character and appearance together with photographs and links to some of the incidents they have been involved with.