H is for... Hart, Captain John (1)

Commander of the Royal Navy base HMS Seaspite. This was situated on the south coast of England, close to where a number of mysterious ship sinkings had taken place. The Doctor arrived at the base unannounced when he heard that a lifeboat from the most recent sinking had been taken there. Hart agreed to take him seriously only after Jo Grant had turned up with their UNIT credentials. The Doctor pointed out the circular scorch marks on the underside of the boat, and drew Hart's attention to the fact that an old Napoleonic seafort was located in the middle of the area where the ships had sunk. Hart grudgingly allowed the Doctor to investigate, sending a rescue helicopter to the fort when the Doctor and Jo were late returning. Initially resistant to accepting that the sinkings were the actions of Sea Devils, marine cousins of the Silurians, the Captain slowly began to come round as more unexplained events took place - such as the theft of electronic equipment from his stores, and an assault on one of his officers, by someone Jo claimed to be the Master - who was supposed to be under lock and key in the nearby special prison run by his golfing friend Colonel Trenchard. The theft took place when Trenchard was visiting the base, and Hart went to the prison to check that the Master was still in custody - unaware that the prison governor was under his charge's malign influence. Hart agreed to send a submarine to investigate the seafort, and was alarmed when contact was lost - leading him to finally take the Doctor's claims seriously. Determined to resolve the situation himself, he was put out that the government sent a civil servant named Walker to take charge. Walker simply aggravated the situation. When the Sea Devils attacked the base, Hart manned a cannon to help repel them. He later managed to get the Navy to delay an attack on the Sea Devil shelter, which gave the Doctor time to escape its destruction after he had sabotaged its power supply.

Played by: Edwin Richfield. Appearances: The Sea Devils (1972).

• Richfield made one further appearance in the programme - as the Gastropod ruler Mestor in The Twin Dilemma. Unfortunately he was entirely covered by mask and costume, and even his voice was treated electronically - so it was a bit of a waste by director Peter Moffatt casting an actor who had been all over British film and television for decades in the role.
• Three of his genre roles include Hammer films Quatermass 2, X The Unknown and Quatermass and the Pit. He was a guest artist in many of the ITC style adventure series - often portraying a villain, but the 1968 TV version of The Three Musketeers saw him playing D'Artagnan.
• He's the only actor - apart from Patrick Macnee - to have appeared in every season of The Avengers.