Valentine Dyall
From Tardis Wiki, the free Doctor Who reference
Valentine Dyall (7 May 1908-24 June 1985) played the Black Guardian in the Doctor Who stories The Armageddon Factor, Mawdryn Undead, Terminus and Enlightenment.
Dyall also recorded the voice of Slarn for the radio play Slipback, which unfortunately was not broadcast until after his death.
He was also one of the few actors considered for the role of the Second Doctor; Dyall, like the other actors, declined the offer to play the role because he didn't want to commit to a long-running role.
