Moyes was born in Dublin on 19 January 1923 and was educated at Overstone girls' school in Northampton. She joined the WAAF in 1939. In 1946 Peter Ustinov hired her as technical assistant on his film School for Secrets. She became his personal assistant for the next eight years. In 1960 she wrote the screenplay for the film School for Scoundrels starring Ian Carmichael, Terry-Thomas, and Alastair Sim. She married photographer John Moyes in 1951; they divorced in 1959. She later married James Haszard, a linguist at the International Monetary Fund in The Hague. She died at her home on the island of Virgin Gorda (British Virgin Islands) on 2 August 2000.
Her mystery novels feature C.I.D. Inspector Henry Tibbett. One of them, Who Saw Her Die (Many Deadly Returns in the US) was nominated for an Edgar Allan Poe Award in 1971. She also wrote several juveniles and short stories.