My other Chiswick Book Festival highlight was a talk by Sonia Purnell about her biography of a woman once described by the Nazis as “the most dangerous of all the female Allied spies”.

Virginia Hall was one of the first female solo spies to enter France during World War II, at a time when M16 weren’t supposed to be hiring women – let alone disabled women. Virginia had a prosthetic leg and “broke all the rules”, proving an incredibly successful agent. Why, therefore, do we know so little about the woman who Sonia Purnell “stumbled across” and who the Nazis “wanted to destroy”?

Virginia was born in 1906 to a “grand” Baltimore family. Her grandparents owned a massive stately home; her mother, Barbara, had been Virginia’s father’s secretary and had ambitions that Virginia, through marrying well, would restore the family to its former social standing. Virginia, however, was a tomboy and loved horses and hunting, disdaining young men. She did, in her teens, get engaged under parental pressure, but eventually ended the relationship.

This tall, athletic free spirit wanted a career, and to travel; her goal was to become an ambassador. Having persuaded her father, Ned, to let her study abroad, Virginia found herself in Paris at the age of 20, attracting many admirers. She fell in love instantly with France’s capital, marvelling at its lack of prohibition and racial segregation and soaking up its philosophers, authors, cafes, painters and bars.

Continuing her studies in Vienna, Virginia found “true love” with a Polish officer named Emil. Her parents, however, were horrified by her choice of beau and Ned forced her to end the relationship.

After Ned lost yet more money in the 1929 Wall Street crash, Virginia returned to America fluent in five languages and despondent over the rise of fascism in Europe. Following in her mother’s footsteps, she became a secretary and was posted first to Poland and then to Turkey.

It was while she was in Turkey that Ned died from a heart attack. Virginia was devastated – and threw herself into the pursuits that she so loved. However, those pursuits were not without danger and, on a hunting expedition, Virginia tripped over a wire fence and accidentally shot herself, with her father’s gun, in the left foot. Gangrene followed – as did an emergency amputation. Worse was to come, as Virginia developed sepsis and nearly died.

Suffering from chronic depression, Virginia returned to America to have a prosthetic leg fitted. Bear in mind that prosthetic limbs, then, were in their infancy: “Cuthbert”, as Virginia named him, was clunky and rudimentary – and his buckle chafed her leg until she bled. Aged just 27, Virginia’s life had changed forever; she found herself unable to walk up steps or even to flex her ankle.

Determined not to be a victim, Virginia went back to work, where she was no longer wanted – tellingly, she was posted to Venice, the home of 400 bridges. Undeterred, she bought her own gondola – and learned how to row it. This was a great time for Virginia professionally; she shone in her job and stood in for all the senior diplomats. Having passed the U.S. diplomacy exams, however, she was told that amputees were barred from becoming diplomats (a blatant lie).

France was invaded by Nazi Germany in May 1940 and Virginia travelled to Paris, desperate to help in whatever way she could. Upon her arrival, the French army hired her to drive ambulances near Metz; just a few days later, the Germans were overrunning France and 10 million refugees were fleeing from the border – with Virginia Hall driving in the opposite direction time and time again, the ambulance’s clutch pressing down on her leg and causing her agonising pain.

After France fell, Virginia travelled to London where she encountered a Special Operations Executive (SOE) agent in an underground station who infiltrated her into Vichy as an American journalist working for the New York Post – to whom she did, indeed, smuggle coded messages. In an act of incredible resourcefulness, Virginia managed to smuggle messages out of France, into Switzerland and to Britain’s Swiss Ambassador.

Having set up a safe house in Lyon, Virginia made two key recruits: Lyon’s convent, and the local brothel madam, Germaine Guérin – and, vitally, the latter’s prostitutes. Guérin did such a brilliant, and brave, job that the British government paid her a lifelong pension. Her girls drugged their clients and rifled through their uniforms for documents which they then photographed. Incredible acts of bravery – and yet, we don’t know any of the prostitutes’ names, although we do know that a number of them were caught and sent to concentration camps, where they suffered terrible fates. Those that weren’t caught were accused, after the war, of being collaborators.

Adding a glimmer of humour to an otherwise terrifying situation, the women obtained ‘VD-free’ cards from their local GP under false pretences and set about sleeping with – and infecting – as many German soldiers as possible.

In a country “gripped by fear and apathy”, Victoria spent much of her time reassuring, encouraging and organising – while she created cells from the Riviera to Paris and beyond, involving police officers, business men and postal workers. This, too, had never been done before – and slowly, but surely, the Germans were closing in on the woman they’d nicknamed “La Dame Qui Boite”, or the “Limping Lady”.

By the end of 1941, Virginia was the only Allied agent in France. All the others had been caught and 12 were imprisoned in a stone fortress, from which it was impossible to break them out. Virginia persuaded her friends in the Vichy government to move the prisoners to an outdoors camp, from where she staged a spectacular jail break escape involving a priest with no legs (he’d lost them in the First World War) who smuggled in a wireless. Concurrently, messages and tools bottled in aspirin jars were smuggled in. The prisoners were sprung out in July 1942 and all twelve of them made it from France to Spain and then to England.

Virginia Hall’s achievements, says Purnell, came about in spite of, not because of, being a woman. She was the only SOE agent to be given a military ranking and no one wanted to take orders from her. Vichy was a conservative regime, where women were expected to stay at home and raise multiple children. Virginia also had to contend with a continual flow of propaganda declaring that Britain was about to fall: there was no evidence to support this, but its continual repetition made it believable.

Virginia’s network was eventually infiltrated by a Nazi priest and she had to escape France during the worst winter for 200 years. The journey across the Pyrenees was gruelling beyond belief, but Virginia made it from Spain, to London and then, would you believe, back to France. This time, she disguised herself as an elderly milkmaid, filing down her teeth, using make-up to create wrinkles on her face, dying her hair and dressing to look stouter.

Virginia Hall’s crowning achievement was to liberate, without the assistance of a single professional soldier, the area surrounding Normandy, at the time of the Normandy landings. Her saboteurs put up misleading road signs to direct troops the wrong way (“preferably over a precipice”), organised parachute drops of weapons, derailed trains, destroyed bridges – and captured 500 German troops.

After her incredible wartime heroics, it would be nice to think that Virginia found happiness – and she did, of sorts. Having fallen in love with a resistance colleague named Paul Goillet, the couple set up home in America, only for Paul to have to hide away for ten years because Barbara disapproved of him. Virginia went to work for the CIA, who treated her “appallingly”; she was sidelined and ignored because they didn’t believe a woman should be allowed to do her role. Only recently has Virginia’s contribution to the war effort been publicly recognised by America – and her portrait now hangs in CIA HQ.

Whilst writing this memoir, Sonia Purnell talked to Virginia’s 89-year-old niece. She shared tales of “Aunt Dindy”, who she remembers as “extraordinary”: fun, inspiring and full of amazing stories – but not cosy (Paul was). Aunt Dindy rarely, if ever, spoke of the war or the vital contribution she made to the Allies’ eventual success; a characteristic, you might argue, that speaks volumes about the character of this incredible woman.