'Brigadier! It's growing!' screamed Sarah.
Still weakened by his third regeneration. the Doctor along with Sarah, the Brigadier and Harry Sullivan, faces the threats made by a group of dissident scientists, including the icy Miss Winters, to enslave the world - or perhaps to destroy the planet entirely.
Written by Terrance Dicks and broadcast in 1974, this story was first published under the title The Giant Robot.
It was the first television story ever to feature the Fourth Doctor, as played by Tom Baker - regarded by many as the definitive Doctor. Robot also introduced Harry Sullivan to the TARDIS crew.