Prisoner (The Mind of Evil)

An unnamed prisoner was an inmate of Stangmoor Prison.

Biography
When Harry Mailer and led a breakout, the prisoner kept guard over the main gate disguised in a prison officer's uniform.

When Brigadier Lethbridge-Stewart, posing as a delivery van driver, arrived at the prison to drop off some provisions, the prisoner allowed him to go in — unaware that inside the van were not provisions but a UNIT assault team. The prisoner was then knocked out by one of the UNIT soldiers. (TV: The Mind of Evil)

Behind the scenes

 * Matthew Walters is credited for episode five as "Main Gate Prisoner" on-screen, and as "Main Gates Prisoner" in Radio Times. He also appears uncredited in episodes three and four.