Edmund Warwick
From Tardis Wiki, the free Doctor Who reference
Edmund Warwick (15th July 1907-21st December 1989) played Darrius in The Keys of Marinus and, wearing a similar wig, stood in for William Hartnell in The Dalek Invasion of Earth after Hartnell hurt himself and could not put in a full appearance. Though he arguably did not resemble Hartnell very much facially, he also played the "Robot Dr Who" in The Chase.
