Brian Proudfoot
From Tardis Wiki, the free Doctor Who reference
Brian Proudfoot is perhaps most significant as the first actor to be featured in location filming on Doctor Who. He was the uncredited double for William Hartnell in The Reign of Terror. He was photographed from the back in long shots in sequences where the First Doctor was meant to be roaming the French countryside on foot.
He later had a credited, speaking role as Tigellinus in The Romans.
