Muriel drew on his own life for material and completed four volumes of autobiography that relied heavily on his youth in Suffolk and Essex.

The son and grandson of physicians, his last book was a true crime work titled Doctors of Murder (1962).

[8] Muriel was a teacher of English at Wisbech Grammar School in the Isle of Ely, one of his pupils was John Gordon.

Jeremy Brooks in The Observer described Muriel and his writing in Essex Schooldays as too well-behaved as he moved in a world of country rectories, hunt-meets, and private schools, the book only livening-up when Muriel finally realised his revulsion by blood sports during an otter hunt.

[10] Andrew Leslie in The Guardian identified a "passionate countryman", nostalgic for the East Anglia of his youth, and a mass of detail that would best please those of a similar inclination.

[12] In "At the Feet of Gamaliel" (1944), Muriel drew on his background as a privately educated child of a middle-class family in what Charles Marriott of The Manchester Guardian described as the story of the "demoralisation and redemption" of a teacher in a preparatory school, told with "insight and humour".

[7] Muriel's biography of George Eliot (1940) was described by Basil de Sélincourt as "as readable as it is risky", with the author a lover of the "broad truth" and strong on human sympathy, confidently describing the vicissitudes of Eliot's life but lacking the finer judgements required by the more discriminating reader.