Sergeant Hart was a UNIT officer who served under Brigadier Lethbridge-Stewart. He was assigned to guard Major Baker in the sickbay of the Wenley Moor nuclear research facility, but Baker tricked him and knocked Hart out.

He was later stationed to guard the entrance to the caves. When Hart lost contact with Private Wright in gallery five, Captain Hawkins decided to go and see what happened, despite Hart's warning that the Brigadier told them to stay where they were.

Hawkins and Hart found Wright's body, but they were ambushed by a Silurian, which killed Hart. (TV: Doctor Who and the Silurians)

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