Guest Stars Nicholas Courtney as Alistair Gordon Lethbridge-Stewart Terence Denville as Cyberman Pat Gorman as Cyberman Ralph Carrigan as Cyberman Charles Finch as Cyberman Derek Chafer as Cyberman John Spradbury as Cyberman Peter Halliday as Packer Kevin Stoney as Tobias Vaughn Sally Faulkner as Isobel Robert Sidaway as Captain Turner John Levene as Benton James Thornhill as Sergeant Walters Edward Burnham as Professor Watkins Ian Fairbairn as Gregory Stacy Davies as Private Perkins