Actress Minnie Driver has opened up about her late father's secret life and family while tracing her roots on a new British genealogy show.

The Good Will Hunting star jumped at the chance to climb her family tree on the Bbc’s hit show Who Do You Think You Are? because she was hoping to unearth details about her shady father's past, after discovering he had lived a double life while romancing her mum.

The actress told producers she knew very little about her dad Ronnie's past and still wishes he had been more open with her before he died two years ago, adding she was desperate to know more when she became a mum to her son Henry four years ago (09).

She says, "Henry made me want to connect with who I really am. I want Henry to have a different experience than I had. Where I come from there are these big gaps and I’d like to fill those gaps for him. I think it’s powerful knowing where you are from."

On the show, Driver revealed her mum, Gaynor Millington, was her dad's mistress, explaining, "My parents met in 1962 and were together for 13 years. They broke up when I was six. During that entire time, my dad was married to someone else and had another family. I didn’t know my parents weren’t married until I was 12 or 13. My dad lived a very split life. We just did not talk about where he came from."

And she tells Britain's Mirror newspaper she only discovered her father was a World War Two Air Force hero when a friend recently bought a book at a sale and found a story about him receiving the Distinguished Flying Medal for bravery in 1939.

That discovery prompted Driver to dig deeper and she started her genealogy quest, which will air on Tv in Britain later this month (Aug13), by chatting with her mother. On the show, she confronts her mum and demands to know the truth about her dad.

Millington says, "It was the classic thing of the married man telling the girlfriend that it will all be fine, if she could just hang around. So I hung around for years.

"I knew he was hiding something but it wasn’t anything I wanted to dig out because I could see it meant a lot to him to keep it hidden. It just didn’t seem too appropriate to dig around in his past."

Reading about her father's heroics as a gunner in the war brought the actress to tears on the show - she discovered he had to put a fire out with his hands in a desperate bid to save his plane, his crew and his life during a daring raid on a German airbase.

He then launched a dinghy when the plane crash landed into the freezing winter waters of the North Sea, and his efforts helped save the lives of three injured crew members. His actions earned him the Distinguished Flying Medal.

Driver says, "It seems unbelievable what he did. It reads like a movie script... I feel very close to a part of my father that I never knew."

She discovered her dad married Annie Wilshaw towards the end of the war and the couple had a daughter, named Susan.

On the show, Driver reveals she learned all about her half-sister while attending a polo match in Windsor, England with her when a family friend remarked, "How delightful to see the family all together." Annie divorced him soon after that revelation.

The actress also unearthed secrets about her grandfather, Charles Driver, who also had a secret life before he wed her grandmother. She discovered he was previously married to a woman named Ada Wood Stancliffe, and the couple had a son, the actor Leslie Stancliffe.

Thrilled Driver says, "I’m so happy, someone who does the same ridiculous thing as me."

Leslie died in 1947, but his daughter - Minnie’s half-cousin Jean - is alive and the show brought the two relatives together.

Jean sent the actress family photographs featuring her father.

Minnie says, "It makes me wonder for my father, why he chose to keep everything so secret. It would have been nice to talk to him about it all."

Ironically, Driver has never revealed the identity of her son's biological father, but the show has prompted her to divulge that he was a writer on her cancelled Tv series The Riches.