Churchill ordered: set Europe ablaze!

In December 1939 a "flaming Polish patriot... expert skier and great adventuress", according to British secret service records, submitted a bold plan to ski into German-occupied Poland. The men laughed when Krystyna Skarbek demanded, rather than volunteered, to be taken on.

Agents were expected to be both British and male. Yet Britain needed to make contact with the Polish resistance - and Skarbek not only spoke the language, she was very well-connected.

She even knew secret mountain ski-routes because, as a bored countess, she had once smuggled cigarettes over the border passes just for the thrill. Too useful to ignore, the British signed her up. "She is absolutely fearless," that first report concluded, although someone would later pencil in the margins: "She terrifies me."

Skarbek, also known as Christine Granville, was not only the first woman to serve Britain as a special agent during the Second World War, she would also become our longest-serving agent, male or female, and among the most effective.

Having established contact with the Poles, she repeatedly smuggled out microfilm of military intelligence hidden inside her gloves. In the spring of 1941, she brought out film-footage of preparations for Operation Barbarossa, the German invasion of Soviet-held territory when Hitler betrayed his former ally Stalin.

This was so explosive that when it reached Winston Churchill, he told his daughter that Skarbek was his "favourite spy".

But her successes were one of several factors that eventually overturned British policy against deploying women on or behind enemy front lines.

After the fall of France in June 1940, Britain established a pioneering organisation to support the resistance there and eventually across the world. The Special Operations Executive, or SOE, established that July, was launched with Churchill's famous order to "set Europe ablaze".

Teams including a circuit leader, courier, wireless operator and sometimes a weapons instructor, would parachute into occupied territory, bringing training, weapons and other supplies plus a vital communications link to London. The resistance could now work to a strategic military plan - particularly vital in the run-up to D-Day.

Prejudice was still so profound, however, that women in the British Armed Forces were not allowed to carry weapons. Yet the maverick SOE had run into a problem. Able-bodied men of conscription age moving around occupied territory attracted attention.

In June 1942 this was compounded when many thousands of French workers were deported as indentured labour for the German war effort. In response, young Frenchmen fled to resistance camps in the countryside, where they became known as the Maquis. A generation were now either in the hills, hiding, PoWs, deported or dead.

Women, however, were still travelling around by train and bicycle, or hitching lifts, trying to keep businesses going and support their families. SOE needed agents who would blend into this wartime population - and Skarbek had already demonstrated how effective women could be in the field. Churchill now nodded through the deployment of women in principle despite military opposition.

SOE's recruiting officer later distinguished what he called the female agents' "cool and lonely courage" from male bravery but, in fact, the women were recruited for the same qualities: their language skills and knowledge of the country they would be sent to. They underwent the same training as the men, starting with intensive paramilitary courses in the Scottish Highlands, fitness, fieldcraft and survival, followed by weapons training, sabotage, armed combat and silent killing, as well as wireless transmitting, Morse and coding.

Many were given parachute training, and then there was tradecraft, such as surveillance, picking locks and losing a tail.

Yet male and female experiences never completely overlapped.

Legally, the men were soldiers; the women seconded civilians. To enable them to carry weapons they were drafted into the First Aid Nursing Yeomanry, the only women's uniformed military organisation outside of the British Armed Forces.

Eventually around 75 women from 13 countries served as SOE agents.

Other than sheer courage, they had little in common. Most were British or French but two were Polish and the rest came from Belgium, Chile, Germany, India, Ireland, New Zealand, the Netherlands, Russia, Switzerland and the US.

Of all faiths and none, and all social classes, several were mothers and at least one a grandmother.

Many were beautiful, although this could be a disadvantage as it made faces more memorable. Despite popular perception, it was not only possible but preferable for female agents to be plain.

Of the 39 women sent into occupied France, Giliana Balmaseva from Chile was the first in 1940. Although untrained, she gathered everything needed to establish an effective escape route over the Pyrenees to Spain. American Virginia Hall was one of many who would later escape this way.

Among other work, Hall organised the jailbreak of 12 captured Allied agents, all of whom made it safely to Britain. A pre-war accident that left her with a prosthetic leg, which she named "Cuthbert", led the Germans to offer a reward for the "limping lady". When eventually she was recalled to Britain, hiking over the Pyrenees despite the pain from her prosthetic, SOE mistakenly advised her: "If Cuthbert troublesome, eliminate him."

Hall would later return to France with the US version of SOE, the Office of Strategic Services (OSS), and eventually joined its spin-off, the CIA.

Nancy Wake was already in France, where she helped run another escape line out of Marseilles. When a five-million-franc reward was put on her head, she took the route herself and joined SOE in London. She parachuted back into Occupied Europe in April 1944. When her chute caught in a tree, the French resister collecting her called up: "I hope that all the trees in France bear such beautiful fruit this year."

"Don't give me any of that French s***," Wake replied.

She went on to arrange the delivery of weapons locally before joining attacks on German installations. Once she killed a German sentry with a karate chop learned during training.

Noor Inayat Khan was the daughter of an Indian Sufi Muslim religious leader. Drafted into SOE from the WAAF (Women's Auxiliary Air Force), she became the first female wireless operator sent to Paris. Despite a series of arrests after her arrival, she insisted on staying. She had several close shaves, including when a German neighbour caught her hanging her aerial from a tree. He helped when she told him she wanted some music.

Eventually, though, Inayat Khan was arrested. Despite refusing to speak during interrogation and twice attempting escape, her captured notebooks enabled the Germans to entrap several more agents. Manacled and beaten, Inayat Khan was executed at Dachau.

Her last word, heard by another guard, was the cry: "Liberté."

Pearl Witherington was born into a British family in Paris, so poor that as a child she sometimes stole food to survive. After the fall of France, and aged just 17, she managed to get to London. There she joined the Air Ministry and was sent to SOE.

Parachuted back to serve as a courier, she spent her first night sleeping on a haystack hiding 20 tons of explosives. After her circuit leader was arrested, Pearl became the only female circuit leader, appointing her fiancé as her second-in-command. When the BBC broadcast instructions for D-Day, "the messages came over to cut the lines and routes and to make havoc," Pearl recalled. "So being obedient, that's what we did."

With a force of around 2,000 maquis, Pearl's units attacked German convoys, hindering reinforcements from reaching Normandy. They eventually forced the surrender of 16,000 German troops.

Krystyna Skarbek was also sent to France in the summer of 1944, where she single-handedly secured the defection of an
entire German garrison on a strategic pass in the Alps.

Discovering that her circuit leader and two other officers had been arrested in her absence, she marched into the prison where they were being held and - exaggerating how close US troops were - terrified the Gestapo officer in charge into releasing
all three men.

Many more female agents served in occupied Belgium, Holland, Italy, Egypt and elsewhere. The brilliant Elzbieta Zawacka, known as "Agent Zo", was the only woman to parachute into Poland.

There she not only established an important intelligence network but also played a key role in the largest organised act of defiance against German occupation in Europe - the Warsaw Uprising.

Of the 75 female agents, 16 did not return.

Three, including Inayat Khan, were awarded the George Cross, Britain's highest award for gallantry not in the presence of an enemy. The rest received a variety of British civil medals. Being women, none were entitled to military honours.

Pearl Witherington succinctly expressed the bitterness many felt, saying "there was nothing remotely civil" about their wartime service. The great irony is that it was lack of recognition that initially made the women so effective - yet even when their service was finally officially recognised, its perceived status was diminished.

Clare Mulley is author of Agent Zo; The Women Who Flew for Hitler; The Spy Who Loved; and The Woman Who Saved the Children