Margaret Blaine

Margaret Blaine was a senior member of MI5 in the early 21st century. Some time before March 2006, Blaine was murdered by Blon Fel-Fotch Passameer-Day Slitheen, who used her skin to impersonate her. (TV: Aliens of London) Still posing as Blaine, by September 2006, Blon ran for mayor of Cardiff. Shortly after, the skin suit made from the deceased Blaine was left vacant in the Doctor's TARDIS when Blon was regressed to her pre-hatched state after looking into the Heart of the TARDIS, with the egg being recovered by the Ninth Doctor. (TV: Boom Town)

Behind the scenes

 * Technically, Margaret Blaine never appeared in Doctor Who, only Blon Fel-Fotch Passameer-Day Slitheen masquerading as her. However, the credits for Aliens of London, World War Three and Boom Town credit the character by her alias of Margaret Blaine.