The captain was the officer in charge of the army detachment summoned by Sir Charles Summer to investigate the warehouse in Covent Garden where the first War Machine was being constructed in July 1966.
After receiving authorisation from Sir Charles, he sent a patrol in to search the warehouse. He briefly spoke with the First Doctor and Ben when they arrived on the scene before the survivors of the patrol fled the warehouse pursued by the War Machine. With the machine jamming their weapons, the captain told Sir Charles they needed to evacuate the area and ordered his men to take cover but the machine shut down, having not been fully programmed.
After taking the WOTAN-controlled workers into custody, Major Green was brought to the Doctor, Sir Charles, the captain and the Minister, only for it to turn out he remembered nothing after being taken over by WOTAN. The captain had him taken away for medical attention after being advised by the Doctor. He later supervised the construction of the cable apparatus the Doctor used to capture the second War Machine. (TV: The War Machines)