Forty-five years after his death, martial arts megastar Bruce Lee is still arguably the best-known Chinese actor in the world.

But behind the yellow tracksuit and the nunchaku, Lee was a complicated character with flaws and foibles.

Martial arts writer Matthew Polly, who also spent two years studying kung fu at a Shaolin temple in China, has attempted to reveal Lee's lesser-known side in his new book Bruce Lee: A Life. During the seven years he researched the book, Polly interviewed people who knew the actor, including Betty Ting – the actress in whose home the movie star was found dead in 1973.

Polly talked to Inkstone about Lee’s struggle with race, a new theory on Lee’s cause of death and why Lee would be unhappy if he were alive today.

Inkstone: Why did you set out to write a biography of Bruce Lee?

Matthew Polly: I was one of those scrawny little kids who saw Enter the Dragon when I was 12 years old. He became one of my childhood heroes. But when a friend suggested that I should write a book about Bruce Lee, I thought it was a stupid idea because there must be several good biographies. But there’s only one English-language biography still in print, and it was written 25 years ago. I kind of felt offended on behalf of Bruce, that no one seems to think that he was important enough to write a proper biography of him. Any white guy in America who does anything gets three biographies. I felt he was ignored because it was kung fu, and that’s considered lowbrow. Partly also because he’s Asian-American, and that ethnic group gets more ignored than others do.

Inkstone: Any surprising discoveries?

Polly: We’ve known for a long time that Bruce Lee was Eurasian, and most people assumed he was a quarter German. His ancestry was actually Jewish. His great-grandfather was born in Rotterdam, the Netherlands, so he had Dutch-Jewish ancestry. His grandfather had an affair with a British woman. Bruce was a quarter English, an eighth Dutch-Jewish and five-eighths Chinese. Sir Robert Ho-tung, the richest and most influential man in colonial Hong Kong, was his great-uncle.

Inkstone: How did Lee look at his mixed heritage?

Polly: He studied martial arts under Ip Man, but some other students didn't like him because he wasn't full-blooded Chinese. He also had a lot of resentment towards the British. When he was in high school, he would pick fights with English boys. Back in the 1950s, a lot of Chinese in Hong Kong believed that the city shouldn't be under colonial rule. When he was 18, he returned to the US where he was born because he got into so many fights, and the police were going to arrest him. When he was in America, he faced racism there. He knew how it was like to be discriminated against by both sides. As a result, he developed an almost post-racial identity. When people asked him if he was American or Chinese, he said, “I think of myself as a human being first.”

Inkstone: Lee’s death at the age of 32 remains one of the biggest mysteries. Did you discover any new evidence?

Polly: You can never know for sure, but my theory is that Bruce Lee died of heatstroke. Ten weeks before his death, Lee collapsed when he was dubbing sound for a movie. They turned the air-conditioning off and it was one of those super hot Hong Kong days. He was saved after being rushed to the hospital. The second time, he laid down and didn’t wake up again. The autopsy found out that he had suffered from brain swelling, which can be caused by heatstroke. About a month before his first collapse, he had his underarm sweat glands surgically removed because he thought sweaty armpits looked bad on film. The overwork also made him physically vulnerable. He had not been able to sleep and had been losing weight before his death.

Inkstone: He was found in actress Betty Ting’s home, and many know that she was his mistress. How did Bruce Lee look at marriage?

Polly: His wife Linda didn’t know about his affairs until he died. Apart from Betty, he had a few more girlfriends. Bruce Lee came from two cultures which didn’t believe in monogamy: One was Hong Kong in the 1950s, and his grandfather had 13 concubines. He went to America in the 1960s during the Free Love era, and Hollywood was never really a conservative place. I think Bruce Lee genuinely loved his wife, and he knew it would hurt her feelings if she found out, so he was extremely discreet.

Inkstone: Do you think that Bruce Lee would be happy about Hollywood if he were still alive?

Polly: I think he would be really angry that there aren’t more Chinese stars in Hollywood. It’s impossible to think of a romantic hero who is Asian. He would be shocked that it is 45 years since he first starred in a Hollywood movie, and yet there still isn’t someone who’s playing heroic, romantic leads – which was what he wanted to do.

This interview has been condensed and edited.