Ken Livingstone

Ken Livingstone was the mayor of London in 2004.

The Sixth Doctor once suggested that he had met Livingstone. (AUDIO: Cryptobiosis)

He met the Eighth Doctor at some point in the 20th century and was aware of the Doctor's dealings with UNIT in preventing alien invasions.

In 2004, the mayor was tied up in his office by Martin and an android duplicate of Livingstone was created in his place. The android allowed the Doctor and his companions into Tate Modern and was responsible for the speech at the opening ceremony of the Tomorrow Windows. During the speech, the duplicate's head split in two, revealing an electron bomb that later destroyed Tate Modern.

The real Ken Livingstone was later found in his office by the police. (PROSE: The Tomorrow Windows)

A member of a crowd shouted out, "It's got to be Ken Livingstone ain't it", in 2006 after a spaceship crashed into the Thames. (TV: Aliens of London)

Behind the scenes
Ken Livingstone is a Doctor Who fan, and appeared in the 1994 documentary More than 30 Years in the TARDIS.