When I meet film actor Dev Patel, he is standing in a bathtub at the QT in Sydney, fully clothed. What’s almost more disconcerting is his accent. It’s British. You would swear Patel was one of us, so brilliantly does he mimic the notoriously tricky Australian accent in his latest film, Lion.

Patel is friendly, easygoing and fun, worlds away from his tortured onscreen character Saroo Brierley, whose story Lion so beautifully and heart-wrenchingly relays.

Few people would have missed the hype surrounding this new Australian film that co-stars Nicole Kidman, Rooney Mara and David Wenham among others, but in this case, the hype has merit.

Destined to be one of the hit films of 2017, Lion is based on the true story of five-year-old Indian boy Saroo, who is separated from his brother and becomes lost in Kolkata, thousands of kilometres from his impoverished home village. Alone and without a word of the local language, Saroo ends up in an orphanage from which he is ultimately adopted by a Tasmanian couple. Years later he befriends some Indians at university and, consumed by questions about his birth family and home country, becomes obsessed with returning to India to find answers.

The story is so extraordinary, it’s hard to believe it’s true. To prepare for directing Lion, his first feature film, Top of the Lake director Garth Davis retraced Brierley’s footsteps in India. He returned to Saroo’s home village, before being confronted by the chaos of Kolkata.

“Standing at Kolkata station and imagining my children lost there was staggering. It’s immensely chaotic, tens of thousands of people on the move, a small person would be extremely disorientated and just imagining an invisible boy in that environment was incredible,” Davis says.

What was also hugely influential for Davis was meeting both Saroo’s adopted mother Sue Brierley, played by Kidman, and his birth mother Kamla. “They’re really the centrepiece of the film,” he says. “These two mothers who loved him.”

Performing alongside Kidman, an Oscar-winning actor, had a profound effect on Patel. Audiences will be familiar with the British actor’s lead roles in Slumdog Millionaire and The Best Exotic Marigold Hotel, in which he plays Indian characters with convincing Indian accents. His role in Lion establishes him as a powerful actor of gravitas.

“Garth calls me up and says, ‘So you know your mum is going to be Nicole Kidman’. It’s not something you hear every Tuesday,” laughs Patel. “She really set the bar and the tone. Garth would have us do these very strange rehearsals that require you to feel like an idiot at times, and you look across the room and there’s Nicole Kidman with her sleeves rolled up, completely submitting herself. It was really inspiring.”

The film is told in a linear fashion, beginning in India then shifting to Tasmania before arcing back. Davis says the six-week shoot in India was one of the most taxing he’s ever done, and required the cast and crew to battle crowds, heat and pollution while navigating narrow alleyways with heavy equipment.

In contrast, Patel found the four weeks in Tasmania peaceful and serene. “You’re surrounded by nature and water and there’s a real tranquillity and calm that centres you. Garth put us in a very reflective space in our minds, and Tasmania as a place allows you to really be introspective. I loved it,” says Patel. “I really have an affinity to all-things Australia, and Tasmania in particular.” Patel recently finished filming Hotel Mumbai in Adelaide, directed by Anthony Maras.

Lion was nominated for four Golden Globes, including best picture and best supporting actor and actress for Patel and Kidman. Little wonder when you consider the Australian creative team consists of Oscar-winning The King's Speech producers Emile Sherman and Iain Canning; Candy screenwriter Luke Davies and Rogue One: A Star Wars Story director of photography Greig Fraser. A nod must also go to local dialect coach Jenny Kent, who helped Patel and his British co-star, Divian Ladwa, perfect the accent.

Davis has just wrapped filming in Italy on his latest feature, Mary Magdalene, also starring Mara. Davis and Patel both welcome the thought of working together again.

“Yeah, if he’ll have me!” says Patel. “Are you kidding?” says Davis. “I’ve got a few ideas, I’m going to take him a bit deeper.”

(Although Lion didn't receive an award, actor Sunny Pawar who plays the younger Saroo stole the show when introducing a clip of the film with lead actor Dev Patel.)

Lion opens in cinemas across Australia on January 19.