But it's Jane Hawking's book about their unique love story that provides the point of view of this film, and Jones admits she was understandably nervous when she went to Cambridge to meet her, shortly after being cast.

Oscar nod: Felicity Jones has been nominated for the best actress award for her role as Jane Hawking.

"I was actually rather intimidated by her," Jones says candidly, her petite balletic frame perched on the edge of a hotel chair in a Toronto hotel suite where she's staying during the festival's premiere of the film. "I had read her book before I went and I just thought, this woman is incredible; she singlehandedly had three children and looked after Stephen for 25 years, pretty much on her own. When I saw her I told her, 'I should bow down to you, you are an incredible lady'. After meeting her I realised what I wanted was just to capture her essence," she adds, "because she was someone who had an extraordinary love and compassion for Stephen but also was a woman who wanted to maintain her own sense of identity and was academic in her own right."

Jane and Stephen were married for 25 years before he left her for his nurse, Elaine Mason, in 1990. Initially devastated, Jane eventually married a family friend and when Hawking's second marriage ended, they resumed a close friendship that continues today. Jones says it wasn't difficult to imagine what they were like during happier times together. "The dynamic was very much set from watching footage of them interacting with each other, because there were a lot of documentaries that were made about Stephen and his life," she explains. "Eddie and I found those moments where we could see how they worked together and we tried to bring some of that to the film, like Jane feeding Stephen wine," she adds. "He loved wine, particularly champagne, so she would feed it to him on a spoon because she knew it was hard for him to swallow the drink."

The ethereal brunette describes her Oscar-nominated co-star Eddie Redmayne as "an extraordinarily unselfish actor" but Redmayne admits that the film provided a unique challenge for his leading lady, whom he met a few years earlier working on separate theatre productions at London's Donmar Warehouse. "Normally as actors when you turn up on stage, you see each other, you see what the location is and you play the scene and go, 'how about we try it this way' or 'maybe we should try this instead' - but virtually every single scene from halfway through this film, I would turn up and go, 'I can't move from here up'," he gestures sadly at his waistline. "So Felicity and I would work like she'd become an extension of my body. It was literally a physical dance that involved a lot of trust."