One morning in June 1943 Jean Overton Fuller’s friend Noor Inayat Khan said goodbye to her and returned to her posting with the First Aid Nursing Yeomanry (FANY). She said she was going abroad. Fuller thought this odd — as she had thought odd Inayat Khan’s transfer to FANY from the WAAF where she had been trained as a wireless operator.

She was never to see her again. As a Special Operations Executive (SOE) agent, Inayat Khan in fact reported to RAF Tangmere from where she was flown in a Lysander light aircraft to a landing ground in the Loire Valley near Angers. From there she made her way to Paris where, even though the Resistance Group she had been sent to join had just been penetrated by the Germans, over the next few months she did valuable work in circumstances always of great peril transmitting information to SOE in London as well as facilitating the escape of Allied airmen brought down over France. In that time she had once shot her way out of an ambush, with Resistance comrades, killing and wounding a number of Germans who tried to detain them.

Eventually her luck ran out. The German security service, Sicherheitsdienst, was closing in on her, and in October 1943 she was arrested and at first held in a cell in the notorious 84 Avenue Foch. From there she actually managed to escape but was quickly recaptured.

She now endured almost a year in confinement, much of it in Pforzheim in Germany in the appalling conditions of what was referred to as Nacht und Nebel (“night and fog”), chained hand and foot in solitary confinement in a tiny cell on what were virtually starvation rations.

Then, in September 1944, with three other women agents, Yolande Beekman, Eliane Plewman and Madeleine Damerment, she was taken to Dachau concentration camp in Bavaria. There, on the morning of September 13, the four women were taken by their captors out into the camp crematorium compound, and told to kneel down in front of a wall. There, holding hands in pairs, they were shot in turn in the back of the neck by an SS man.

After the war Fuller set out to discover exactly how her friend had met her fate. Her researches, at a time when very few official papers were available, eventually resulted in the book Madeleine (Inayat Khan’s codename in the field), which was published in 1952. In the meantime, in 1946 Inayat Khan had been posthumously awarded the Croix de Guerre with Gold Star, and in 1949 the George Cross by the British Government. Fuller’s book was republished in 1988 with added material, and was long considered to be the definitive biography of this remarkable SOE agent.

This was to be the first of a series of studies on the history of the SOE in France and the penetration by the Nazis of its radio networks. These included Double Webs (1958), Double Agent (1962), The German Penetration of SOE: France 1941-1944 (1975), all of which tended to be highly critical of the British authorities, and Dericourt: The Chequered Spy (1989). Henri Déricourt was one of the enigmatic people whose career she unearthed in her inquiries into wartime espionage and counter espionage. His role was apparently of vital importance to the Resistance but he was thought by many to have been a double agent. In her book, Fuller took his side against his detractors.

Jean Violet Overton Fuller was born in 1915. Her father, a captain in the Indian Army, was killed in the First World War before her birth and she was brought up by her mother, Violet, an artist, and her grandfather, leading a peripatetic life in hotels and boarding houses for part of her childhood.

On completing her education Fuller was set on a stage career and joined a succession of repertory companies, the final one in the hands of the blood-and-thunder actor Tod Slaughter. She decided the stage was not for her.

In 1937 she submitted a poem to The Poet’s Corner in the Sunday Referee and was drawn in to a group around the paper’s poetry editor Victor Benjamin Neuburg, who was encouraging such young talents as Dylan Thomas and Pamela Hansford Johnson. Between 1906 and 1914 Neuburg had been an associate of Aleister Crowley, the hedonist and sorcerer, and had been initiated into his occult order, the AA.

Fuller’s life took a new turn when she met an antiquarian bookseller, Timothy d’Arch Smith, to whom she later dedicated several of her books and with whom she set up a small bookselling business in 1969. In 1965 she published The Magical Dilemma of Victor Neuburg and this was followed by well-received critical biographies of Shelley (1968) and Swinburne (also 1968). A move from London to the borders of Northamptonshire and Bedfordshire provided her with opportunities to master accomplishments not perhaps usual for a woman in her sixties. She learnt to ride; to play the piano; and (after 277 lessons) to drive a small red Fiat which she called Robin.

She continued to publish: on the founder of Theosophy, Blavatsky and Her Teachers (1988); on the Theosophists’ demitted messiah, Krishnamurti, The Wind (2003); on one of their “Masters”, The Comte de Saint-Germain (1988), and an addition to the Bacon-Shakespeare controversy, Francis Bacon, a biography (1981).

Fuller’s mother had been friendly with Florence Humphry Holland, a friend of the painter Walter Sickert (who in the 1930s had attended at Collins’s music-hall Tod Slaughter’s production of Maria Marten or The Murder in the Red Barn with the young Fuller in the role of Maria’s sister Nan). As a result Fuller was persuaded that Sickert was Jack the Ripper, a theory not altogether new but enhanced by family documents. Her book Sickert and the Ripper Crimes (1990) is still in print.

In her last years she wrote a spirited and entertaining autobiography, entitled Driven to It.

Jean Overton Fuller, biographer, poet and painter, was born on March 7, 1915. She died on April 8, 2009, aged 94