Sir Clive Reeves was the British Home Secretary in 1966.
One day while at work, an alien artefact found its way into Sir Clive's briefcase. During a long conversation with the Eighth Doctor, the artefact was stolen by Sir Clive's secretary, Anne Caisson: the Doctor had requested she do this for fear the artefact could corrupt even someone as moral as Sir Clive. (PROSE: For the Man Who Has Everything)
Behind the scenes
Clive is a fiction stand-in for the real 1966 Home Secretary, Roy Jenkins.