Operation Graffham

Operation Graffham was a deception tactic during World War II involving the London Controlling Section (LCS), aimed at convincing Nazi Germany that the Allies intended to invade Norway. (AUDIO: Operation: Hellfire)

Behind the scenes
In the real world, Operation Graffham, part of the much wider Operation Bodyguard, was planned in 1944. Operation: Hellfire is set in 1943, so the Doctor's brief discussion of "Graffham" with members of the LCS, who are apparently familiar with it, is an anachronism.