Bert Walker was the landlord of the Cloven Hoof in Devil's End. Like many of the male residents of the town, he was in the thrall of the Master and a member of his Satanic cult. He was sent by the Master to kill the Doctor after Tom Girton's attempt failed. Bert shot at the Doctor with a sniper rifle, but missed him.
Later, he pulled a gun on the Doctor at the town's May Day festival and attempted to convince the townspeople who weren't involved in the Master's cult that the Time Lord was a witch and should be burned at the stake. He was defeated when the Doctor used Bessie's remote control to "summon" the car, knocking Bert over with it.
Shortly after this, when the Master and the other cult members were summoning Azal in the church, Bert escaped and and tried to return to the church, only to encounter Bok. Although Bert tried to convince the gargoyle he was its ally, Bok promptly disintegrated him.