There's an old adage in film-making: Don't work with your partner, or with pets. But Luke Treadaway broke both taboos to star in A Streetcat Named Bob, the heart-warming true tale of James Bowen, a homeless heroin addict whose life is spiralling out of control - until he befriends a stray cat, Bob, and falls for his neighbour, Betty, played onscreen by his off-screen, real-life girlfriend, Ruta Gedmintas.
"Yeah, I must have been mad to agree to do a film with my girlfriend and a cat," Treadaway laughs. "But when I read the script, I knew I had to do it. It's an amazing story, with an almost fable-like element to it because, at his lowest point, James sows the seeds for his own future by spending the last of his money taking Bob to the vet, to get him healthy again. In that moment, he turns his life around and begins a magical journey."
That magical journey, first recounted in Bowen's best-seller autobiography, makes for both a compelling, feelgood film and a real tear-jerker, as it recalls his struggle to crack his addiction, get off the streets and start anew.
It also focuses on how rescuing Bob helps Bowen rescue himself, with Bob becoming his loyal sidekick - and Internet sensation - when he climbs on his shoulders as he busks in London's Covent Garden.
"We were filming the busking scenes and none of the cats we'd trained for the film would sit still. They just kept wandering off," reveals Treadaway. "Suddenly, Bob jumped off James' shoulder, strolled over to me, sat down in my guitar case and fell asleep. It was like he was saying; 'no one should play me, except me.' From that moment, we had our Bob - the real one!
"We used the real Bob a lot of the time," he adds, smiling. "Most of the time you see a cat on my shoulder, in my flat or in the busking scenes it's Bob. Actually, the only times it's not Bob are the stunt scenes because Bob was a natural - as he was just doing what he's used to doing. Bob didn't always play ball though: sometimes it required little tricks to keep him interested, like tapping cans of cat food behind the camera, to make sure he looked the right way!"
To try to ensure his own performance was just as real and sympathetic, Treadaway decided he needed to fully immerse himself in his role. Consequently, he visited addiction clinics to talk to drug users, took up busking and even slept on the streets.
"When people watch this film I want them to feel that it's an authentic portrayal. I don't want it to look like I've just made a film version of the book and painted it with broad brushstrokes," he asserts. "It would be a joke if I just turned up and tried to pretend I was a homeless person, if I'd never even experienced that.
"That's why I asked James if he'd take me out on the streets, to show me what it's like, how he approached strangers for money and where he'd bed down for the night," explains Treadaway. "I'll never pretend to truly know what it's like to be homeless but to get a little taster of it - and to know the feeling of being damp and cold in the morning, as you pack all your possessions up in a little bag - was something I wouldn't have guessed, or known, without doing it."
"That night also made me appreciate how lucky I was to have a bed to go back to and what a very different feeling it would be if you didn't," he adds, sighing. "Some people don't have that luxury, they don't have any escape. That's a very sobering thought."
The result is a convincing, heartfelt, reflective and - ultimately - uplifting experience as Treadaway charts Bowen's journey in-and-out of addiction, his struggle on the streets and his final salvation, courtesy of a little help from his furry friend, Bob.
"Everybody gets knocked down sometimes and it's how - or if - you pick yourself up that really defines you as a person and determines your future," Treadway says. "The strength that James showed to do that and to fight through his struggles and addiction is inspiring. Obviously, having Bob there helped, but it would be wrong to say it's just because of Bob. It's also about him finding that strength within himself, which James managed to do. That's what's so remarkable and inspiring about his story and about this film."
Who: Luke Treadaway plays James Bowen
What: A Streetcat Named Bob
When: In cinemas today