The Doctor and Jo are trapped on the fort by a Sea Devil while the Master convinces Trenchard to help him steal some electronic components.
Did You Know?
This serial was the first Doctor Who story to involve the Royal Navy in production, as opposed to the Army in previous episodes. When the RN was approached, the production crew was invited to shoot during naval exercises. It proved a mutually beneficial arrangement: the RN got excellent publicity for their participation, while the production received free access to Naval facilities, ships and equipment with a large number of military personnel as volunteers eager to appear on television. The fact that the then current series star, Jon Pertwee
, was a veteran naval officer himself resulted in very pleasant encounters with the sailors eager to meet him. See more
The helicopter sent to rescue the Doctor and Jo from the sea fort is a Westland Sea King when it leaves base. However, the helicopter that arrives at the sea fort is a Westland Wessex. See more
The BBC wish to acknowledge the help given to them by the Royal Navy in the making of this programme See more