Audrey Hepburn was a 'Battle-hardened badass', according to her son Luca Dotti

Audrey Hepburn has been described as a 'Battle-hardened badass' by her son Luca Dotti - and it's not just a reflection of some of her feisty on-screen characters.

As one of the most iconic actresses of her time, the Breakfast at Tiffany's star came across as naive in the 1961 hit movie but in real life, she was as feisty as her character, Princess Ann in the 1953 film Roman Holiday.

Her enduring appeal warmed hearts across the world and Audrey will forever be known as the dark-eyed darling of the Golden Age of Tinseltown who later championed humanitarian work up until her death from colon cancer, aged 63. But now for the first time, her dangerous work for UNICEF has been uncovered in Robert Matzen's new book which fans will be able to read on some of the best Kindles when it's released later this year.

And ahead of its release, it's Audrey's son Luca's views of his late mother that are perhaps the most surprising yet heartfelt. In summing up the star, he told PEOPLE, "The stories she brought back home and shared with us were chilling but always sugarcoated until Warrior totally challenged my perspective. Mum was more than a steel-butterfly; she was a battle-hardened badass, and Warrior: Audrey Hepburn finally tells that story."

Luca explained how his mother's 'most important' mission was being covered in-depth for the first time. He said, "There are hundreds of books about my mother and each in its own way tries to solve a piece of the Audrey puzzle. Some are instant classics while others are merely exploitative, and until now none has focused on what she considered her 'most important career' — her fight for children in need in what she called the Developing World, often in war zones."

He recalled how his beloved mother was expected to be a "pretty princess" for UNICEF but in fact "What they really got was a badass soldier," Luca admitted, as it's revealed Audrey went on multiple trips to dangerous areas across the globe including having witnessed "hell on earth" in Somalia, facing bombs and bullets.

Having almost died of starvation as a teenager living in Holland during World War II, Audrey left it until later on in life to become a parent herself. When she was 38, and raised her two sons, Sean Hepburn Ferrer, now 60, whom she shared with ex-husband Mel Ferrer, and Luca, now 51, whom she shared with ex-husband Andrea Dotti - quietly in Switzerland. 

But fast-forward 10 years and she returned to the organization that helped her during the war when she became an ambassador for UNICEF.

Meanwhile, Biographer Robert Matzen, said, his latest book provides fans with "some answers" as to why fans love her so much. "This is a down-to-earth, funny and fearless Audrey Hepburn, this too-thin waif of a woman charging into war zones at age 60 and beyond, standing in front of cameras with starving children and mothers not to publicize herself, but to bring the world's attention to life-and-death situations."

He added, "Somalia, in particular, is gut-wrenching as Audrey 'went to hell' as she phrased it and while there she stunned seasoned U.S. military men with her courage under fire."

Robert Matzen, the author of the 2019 bestselling biography Dutch Girl: Audrey Hepburn and WWII, has written a new book about the actress called Warrior: Audrey Hepburn and it will be published by GoodKnight Books on 28th September.