The investigation into a “vile joke” about the Queen was sparked by a retired civil servant.

Stan Rosenthal, from Lindfield, near Haywards Heath, said he was “outraged” after comedian Frankie Boyle made a comment about the monarch on BBC2’s topical comedy show Mock The Week.

The BBC Trust, the broadcaster’s governing body, admitted his joke was “sexist and ageist” and would have offended many viewers.

It decided the joke did not breach guidelines because it was well after the 9pm watershed and within audience expectations for the show.