The story establishes that the Brigadier retired from U.N.I.T. in 1976, and that all of his U.N.I.T. appearances predate this story. However, the very first U.N.I.T. story, Season 6's The Invasion, can't be set earlier than 1978! (See The Invasion and Season 13's Pyramids of Mars for more information.) Eric Saward, script editor for this story, later conceded that the 1977/1983 dates used were a mistake.