James Quinlan
Sir James Quinlan was the British Minister for Technology. He conspired with General Carrington to capture three aliens, hoping to have the political coup of making first contact; he used his power and influence to stymy UNIT's investigations, as they were an international body and not a British one. The Third Doctor was aware that Sir James was involved.
Carrington later had one of the aliens kill Sir James, in order to cover his tracks. (TV: The Ambassadors of Death)
Before he died, he received a letter from the Apocalypse Clock which predicted the exact date and time of his death. (AUDIO: The Last Post)
After his death, British space defence was taken over by Sir John Sudbury of C19. (PROSE: The Scales of Injustice)