The Australian star, who became an overnight heartthrob when he was cast in Home & Away before the blockbuster Thor franchise catapulted him to global fame, has shifted his priorities since he became a father of three under three - daughter India Rose and twin sons Tristan and Sasha. A dedicated patron of non-profit organisation Australian Childhood Foundation since becoming a father, Hemsworth is equally passionate about his charity work as his acting career.

Last night, the man who could have been Miley Cyrus' brother-in-law hosted an advanced screening of his new movie, In the Heart of the Sea, with Audi in Sydney to raise much-need funds for the foundation, which provides counselling services and resources to children suffering abuse. A newly minted Audi Australia brand ambassador (joining the ranks of Hugh Jackman and Mick Fanning, among others), it was Hemsworth's idea to use his star wattage for a charity event as epic as the new film. "We're expecting everyone to dig deep so that we can reach our goal of building a Trauma Recovery Centre for Children in Sydney," he says.

A date with Thor: Chris Hemsworth on why he needs to do more than act

"I had the greatest childhood but my parents both worked in the field of child protection and actually for this particular charity, so I was always aware that our experience wasn't the case for everybody," Hemsworth tells me. "So that was what motivated me to get more involved with the issue. Along with his brothers Liam and Luke, Hemsworth grew up between Melbourne and the Northern Territory, where his father was stationed as a social worker - a very different life to the one the three famous brothers now enjoy.

Hollywood's hottest siblings share a healthy rivalry when it comes to fighting for film roles, Hemsworth admits. "It's a business, this business is full of enough ups and downs and inconsistencies but I think what's good for me is good for Liam and vice versa," he says. "We're all very supportive of what we do and there's no direct competition anyway, as much as it might seem that way, the amount of things that need to align for you to get a job is crazy."

A date with Thor: Chris Hemsworth on why he needs to do more than act

It doesn't seem to have been a problem for Hemsworth, who sits high on Forbes' list of the highest-earning actors and is following In the Heart of the Sea with another Thor movie, which begins filming in Australia next year. He had to shed a hefty amount of weight (all those Thor muscles) for In the Heart of the Sea, a process he describes as "aggressive." "We didn't sit at that low weight for more than a week and a half," he says.

Hemsworth has ditched the glittering lights of LA for a quieter life in Byron Bay, where he lives whenever he's not filming with his wife, actress Elsa Pataky, and their three kids. "We moved back to Australia 12 months ago and we were there for a couple of months and then took off with work again," he says.  "It's about trying to schedule enough time to be back here to regain our sanity and resettle - it's pretty hectic on the road, especially with a big family, but we make it work, we're all together and the kids have a great time."

Just don't expect him to throw it all in and open a surf school in Byron any time soon. "I love acting," he says. "I do it for a period and it's exhausting and I pour my heart and soul into it and then I think okay that's it, I need a break, and then a week or two goes by and I get some sleep and I'm like, okay when's the next one, I'm off again." 

A date with Thor: Chris Hemsworth on why he needs to do more than act