The brave secretary branded 'a slow learner' who became one of Britain's top female wartime secret agents

But secret papers released yesterday revealed how former secretary Pearl Cornioley became one of Britain's top wartime agents whose charisma and "colossal bravery" caused havoc for the Nazis.

After being parachuted into occupied France, the 29-year-old went on to organise a resistance unit of 3,000 men who she led on daring guerilla attacks on German troops and supply lines.

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She was also reunited with her pre-war French fiance, who had joined the struggle against the Nazis, leading to a love affair that is thought to be an inspiration for the Sebastian Faulks' novel Charlotte Gray.

When the fighting ended in Europe one senior officer recommended her for the military cross, describing her story as a "true romance" and explaining "our pride and esteem for this gallant girl is very great".

Yesterday, with the release of MI6 documents at the National Archives in Kew, the full story of her extraordinary bravery was revealed for the first time.

Mrs Cornioley was born in Paris to expat Londoners and led her three sisters and widowed mother to freedom in England after Germany invaded.

In London she worked as a secretary in the Air Ministry, but was desperate to see action and convinced the Special Operations Executive - the forerunner of MI6 - to take her on.

She excelled at shooting - and was described as "probably the best shot (male or female) we have had yet" - but the final report by the commander of her training base was damming.

He wrote: "She is of average intelligence and fairly practical, but rather slow in picking up new ideas.

"She is loyal and reliable but has not the personality to act as a leader.

"She would best be employed as a subordinate under a strong leader in whom she had confidence."

Despite this, after only three practice jumps she was parachuted into France in September 1943, carrying a revolver and with secret documents to deliver to a resistance fighter sewn into the hem of her skirt.

Using the codename "Marie", her initial mission was to make contact with a French leader and turn his "rabble" into an army to help the Allies before and after the D-Day landings.

But when the commanding officer of the unit was arrested by the Gestapo, she took control of the unit and helped built it up in strength from forty men to 3,000.

One of the documents described how, from a secret base deep in woods, she was "responsible for numerous ambushes and was continually harassing the enemy."

It added: "Soon after D-Day her group was attacked by two thousand Germans using artillery and maintaining the engagement for 10 hours.

"In this action the enemy lost 86 men and her resistance unit 24, but the Germans succeeded in their object of breaking up the group, and she had to reorganise from the beginning.

"She began guerrilla action on a large scale, causing havoc among German columns passing through the area to the battle front."

She was so feared by the Nazis that a bounty of one million francs on her head and wanted posters displaying her picture were put up around France.

In one despatch from the front smuggled back to London, she described the tremendous dangers they were under if captured.

She wrote: "The Germans were active at the slightest provocation and set fire to many farms and villages. Their treatment of (resistance fighters) when they caught one was appalling.

"After killing them they would proceed to atrocious mutilation beyond recognition."

Despite the risks she kept fighting and her efforts have believed to have encouraged 18,000 enemy troops to surrender.

At the end of the war she was recommended for the Military Cross, with her citation describing how her "outstanding devotion to duty had accomplished a most important task."

But she was left bitterly disappointed when she was only offered a civilian MBE.

In a letter to the Air Ministry, she rejected the award, complaining: "The men have relieved military decorations, why this discrimination with women when they put the best of themselves into the accomplishment of their duties?

"I must say that the MBE looks puny. If I wear a decoration, I wish to be proud of it."

Her complaints were ignored, and instead another senior officer wrote a letter that praised her "colossal bravery" in leading her unit, before adding: "I recommend a bonus of £50."

After the war she finally married her lover, Henri. The couple settled in Chateauvieux, South West France and she had a daughter.

In 2001, she was finally given her long overdue military honours when two British officers presented her with her parachute wings. She died last month, aged 93.