Molly Lefebure was born in London, the daughter of Charles Hector Lefebure and Elizabeth Cox, and was educated at the North London Collegiate School. She went on to study at King's College London at the University of London where she met her husband, John Gerrish. During World War II she worked as a newspaper reporter for a London newspaper. During the war she met Dr Keith Simpson (the pathologist) and worked for him as his secretary where she gained information for her first book Evidence for the Crown, the inspiration for the two part ITV drama Murder on the Homefront. She went on to live with her husband and her two children at Kingston-upon-Thames by the river.
Her children's books include illustrations by the famous Lakeland author, hill walker and illustrator Alfred Wainwright.
She was a Coleridge scholar. After studying drug addiction at Guy's Hospital in London for six years, she wrote a biography of Coleridge that researched the effect on his life of his addiction to opiates.
- Evidence for the Crown: Experiences of a Pathologist's Secretary, London: W. Heinemann, 1955; Philadelphia and New York: J-B. Lippincott Company, 1954, 1955, also published as Murder on the Home Front: The Unique Wartime Memoirs of a Pathologist's Secretary, London etc.: Grafton Books, 1990, ISBN 0-586-20854-2
- Murder with a Difference: The Cases of Haigh and Christie, London: W. Heinemann, 1958
- The English Lake District, London: B.T.Batsford Ltd, 1964
- Scratch and Co - The Great Cat Expedition, with drawings by A. Wainwright, London: Victor Gollancz, 1968; New York: Meredith Press, 1969, ISBN 978-0-9547213-1-2; Blackburn: Mountainmere Research, 2006, ISBN 0-9547213-4
- Cumberland Heritage (Chapters include Camden, Braithwaite, Millbeck, Fellwalkers, Carlisle Canal, Armboth, John Peel (Farmer) and The Blencathra), with endpaper maps of old Cumberland, London: Gollancz, 1970, ISBN 0-575-00376-6
- The Hunting of Wilberforce Pike, illustrated by A. Wainwright, London: Victor Gollancz, 1970
- The Loona Balloona, Nashville, Tennessee: Thomas Nelson Inc., 1974, ISBN 0-8407-6378-6
- Samuel Taylor Coleridge: A Bondage of Opium, New York: Stein and Day, 1974, ISBN 0-8128-1711-7 and London: Victor Gollancz, 1974, ISBN 0-575-01731-7
- Cumbrian Discovery, London: Victor Gollancz, 1977, ISBN 0-575-02235-3
- The Bondage of Love - A Life of Mrs Samuel Taylor Coleridge; London: Victor Gollancz, 1986, ISBN 0-575-03871-3
- The Illustrated Lake Poets, 1987, ISBN 0-7112-0477-2
- Blitz!, London: Victor Gollancz, 1988, ISBN 0-575-04306-7, also published as We'll Meet Again, London etc.: Grafton Books, 1990
- Thunder In The Sky, London: Victor Gollancz, 1991 ISBN 0261669990
- Thomas Hardy's World: The Life, Times and Works of the Great Novelist and Poet, London: Carlton Books Ltd, 1997 ISBN 1-85868-245-2
- Private Lives of the Ancient Mariner: Coleridge and his Children, The Lutterworth Press (2013), ISBN 9780718893002.
- Oliver Gerrish (2013-03-13). "In memory of Molly Lefebure". Retrieved 2013-04-18.
- "Obituary: Molly Lefebure". Daily Telegraph. 2013-04-18. Retrieved 2013-04-18.
- Molly Lefebure, thePeerage.com.
- Cumberland Heritage.
- "Royal Society of Literature All Fellows". Royal Society of Literature. Retrieved 9 August 2010.