He is most known for his central role in founding the Information Research Department (IRD), a secret wing of the Foreign Office dedicated to Cold War propaganda.
According to a long time associate, Claud Morris, Mayhew had "ghost-written some of the most powerful speeches of Ernest Bevin'.
In 1971, with fellow MP Dennis Walters and publisher Claud Morris, he launched a bi-monthly journal, Middle East International (MEI).
Over its thirty-four years MEI had a number of retired British diplomats serving as directors, including James Craig and Anthony Nutting.
[11] In 1973, Mayhew offered £5,000 to anyone who could produce evidence that Nasser had stated that he sought to "drive the Jews into the sea".
Mayhew repeated the offer later in the House of Commons (Hansard, 18 October 1973) and broadened it to include any genocidal statement by any responsible Arab leader (The Guardian, 9 September 1974), while reserving for himself the right to be the arbiter of the authenticity of any purported statements as well as their meaning.
[2] In the general election in October 1974, Mayhew contested Bath instead of Woolwich East in order not to split his former constituency party.
He wrote several books, including Publish It Not: The Middle East Cover-Up (co-written with Michael Adams, 1975) and his autobiography, Time To Explain (1987).
In 1955 Mayhew took part in an experiment that was intended to form a Panorama special for BBC TV, but was never broadcast.
Under the guidance of his friend Humphry Osmond, Mayhew ingested 400 mg of mescaline hydrochloride and allowed himself to be filmed for the duration of the trip.