A British spy who helped lead the French Resistance during the Second World War outfoxed the Nazis by concealing secret messages in the hem of her skirt, according to records unsealed Monday.

Britain's National Archives opened its records on Pearl Cornioley, then Pearl Witherington, who parachuted into France, posing as a cosmetics saleswoman, to deliver coded messages to Resistance members. The release of the records follows her death on Feb. 24.

The records shed light on a woman who quickly adapted to life as an agent but never forgot about her family back home, requesting in handwritten notes that officials in London send her mother and sisters birthday and Christmas presents.

The National Archives released two packets of information, detailing Cornioley's training as a special agent, her activities in the war and her struggle to have her service recognized by the government.

Cornioley, whose nom de guerre in France was Genevieve Touzalin, was educated in Paris. She escaped France ahead of the Nazi invasion and returned to Britain via Spain.

Upon returning to Britain, she worked briefly at the Air Ministry but used her French to gain a slot as a Special Operations Executive agent — one of about 40 women to serve. The Special Operations Executive evolved into today's Secret Intelligence Service, also known as MI-6.

Early in her training with the Special Operations Executive, supervisors said she lacked the natural moxie to excel as an agent, but she compensated with her social nature, innate skill with weapons and useful memory.

"She is of average intelligence and fairly practical, but rather slow in picking up new ideas. She has, however, a good memory and does not forget what she had learnt," a review of her training says. "Outstanding shot with pistol and other weapons. Probably the best shot (male or female) we have had yet."

After parachuting into France, Cornioley passed on secret messages to her first handler in France that she had carried in the hem of her skirt. The documents seen by an Associated Press reporter did not detail what the messages contained.

Following the capture of her leader, she assumed control of the cell in the north Indre department of the Loire River valley, about 385 kilometres southeast of the Normandy beaches.

1 million franc award offered for capture

She interrupted the Paris-Bordeaux railway line more than 800 times and attacked convoys in June 1944, the month of the D-Day invasion. All told, she led 3,000 French Resistance fighters in a host of guerrilla warfare missions.

She proved so crucial that the Nazis issued a one million franc award for her capture, hoping to quash her pivotal role in the Resistance.

"She's obviously a very brave woman. She goes through Gestapo lines, helps airmen escape to safety and baffles the Nazis in the field," said Mark Dunton, a historian specializing in the Second World War and the ensuing decades.

The records also detail Cornioley's struggles with what she considered prejudices against women. She refused a British government award for extraordinary service to the country because the honour was for civilians rather than military personnel. She alleged the government refused women military honours on the basis of sex.

"She's really standing up for women," Dunton said of the evidence in the records.

Later in life, she was showered with recognition.

Queen Elizabeth II made her a Commander of the Order of the British Empire in 2004 in Paris, where she lived. Two years later, Royal Air Force officers presented her with coveted parachute wings at her Paris retirement home. She also received France's Legion d'Honneur.

She met and fell in love with Henri Cornioley, a French prisoner-of-war who escaped and joined the Resistance. They married in a quiet London ceremony after the war and spent the rest of their lives in France. He died in 1999.