The Avengers S03 E06 November Five

"Mrs Peel, We're Needed!"

Michael Dyter, the newly elected MP for South-East Anglia is shot shortly after making his acceptance speech in which he had threatened to expose a major scandal involving the government. Steed knows that the subject of this was the recent theft of a nuclear warhead near London. So was Dyter killed to keep him quiet, and if so, by whom?