Margaret Blaine

Margaret Blaine was a senior member of MI5 in the early 21st century. Some time before April 2006, Blaine was murdered by Blon Fel-Fotch Passameer-Day Slitheen, who used her skin to impersonate her. (DW: Aliens of London) Still posing as Blaine, Blon ran for mayor of Cardiff. (DW: 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.