She was a glamorous countess and British spy whose extraordinary wartime heroics included skiing out of Nazi-occupied Poland with the first evidence of Operation Barbarossa – the Nazi plans to invade Soviet Russia.

Later in the war she played a role in the liberation of France as first contact between the French Resistance and Italian Partisans, and single-handedly secured the defection of a strategically important German garrison.

But the name and achievements of Krystyna Skarbek, the first and longest-serving female special agent in the second world war, are still little known. Now a bronze bust of her will stand in the Polish Hearth Club in London.

The unveiling on Tuesday evening has been organised by the writer Clare Mulley, who wrote Skarbek’s biography, The Spy Who Loved, published in 2013.

The new bust illuminates a remarkable life, one of tremendous valour but also tragedy, which ended with Skarbek’s murder in 1952.

“She was a remarkable woman, it is ludicrous that she is not better known,” said Mulley. “That is not to take anything from all the other women and men who served, all their stories are fantastic, but her story is incredible and she has just not been honoured as she should be.”

Skarbek, a Polish countess who would later use the name Christine Granville, was so incensed by the Nazi invasion of her native country that she demanded that the Secret Service take her on.

It did, and among her many adventures and achievements was managing to get hold of microfilm that was the first evidence of Operation Barbarossa, the Nazis’ preparations for the invasion of its supposed ally, the Soviet Union.

She skied out of Poland with footage – hidden in her leather gloves – that landed on the desk of Winston Churchill. He became an admirer, calling her, according to his daughter Sarah, his “favourite spy”.

In 1944 she was parachuted into France as part of a Special Operations Executive team preparing the way for liberation forces. She made the first contact between the French Resistance and the Italian Partisans, and, acting alone, secured the defection of an entire German garrison in an important Alpine strategic pass.

Later she learned of the arrest of a senior SOE colleague and two French Resistance officers. They were due to be shot and, after Skarbek failed to have them properly rescued, she cycled 25 miles to the German camp and bullied the senior Gestapo officer into keeping them alive.

“She basically terrified him with exaggerated claims of how soon the allies would be there and how she would get him shot if the men were not released,” said Mulley.

After the war, Skarbek was treated appallingly by the British authorities, who initially refused her citizenship even though she was unable to return to the now Soviet-controlled Poland.

“One of the last bits of paper in her files at the National Archives includes a line from the British that said ‘she is no longer wanted’. It is just extraordinary. That is a direct quote,” said Mulley.

Skarbek eventually shamed the authorities into giving her citizenship, but times were hard for her and she was forced to get a job as a bathroom steward on passenger liners. “She is cleaning toilets whereas previously she was a countess who travelled first-class.”

All of the crew were encouraged by the captain to wear their war medals, so Skarbek wore all of hers, including an OBE, the George Medal and the French Croix de Guerre.

No one believed this foreign, probably Jewish, woman could possibly have such medals and she was treated terribly apart from by one steward, Dennis Muldowney, with whom she is thought to have had a relationship.

When they returned to London the friendship soured, but Muldowney was unable to accept rejection. He stalked her and confronted her at the Shellbourne hotel, stabbing her though the heart with a combat knife.

The idea for a bust at the Polish Hearth Club, a place Skarbek would visit after the war to dance and regale officers with her stories, came from Mulley.

It has been made by her husband, Ian Wolter, and includes soil from Poland and the park in London where Polish special forces were trained. “She is literally cast in the soil of her native country and the country she adopted after war, countries she fought so hard and courageously for. I think it is beautiful,” Mulley said.

After the biography and the bust may come the film, with the book rights sold and talk of Angelina Jolie being interested in the story. “Fingers crossed … I want a worthy, brilliant film, I really want her honoured properly,” Mulley added.