A minister was the head of a government department. Ministers of the British government were based in Whitehall. (HOMEVID: The Devil of Winterborne) Senior ministers comprised the Cabinet. (TV: World War Three)
Sir Richard Stevenson was a minister of the Ministry of Defence to whom P.R.o.B.e. was answerable until he was replaced by Brian Rutherford, who was forced to step down due to his connections to BEAGLE. (HOMEVID: The Devil of Winterborne, Unnatural Selection) He was, in turn, replaced by Patsy Haggard, who was later promoted to work closer with the Defence Secretary before resigning. (HOMEVID: Ghosts of Winterborne, When to Die)
Sebastian Vaughan's father was promoted to Cabinet minister after some time working for the Ministry of Defence at Lodmoor Research Facility. (AUDIO: The Vigil)