Luke Treadaway is an Olivier Award-winning actor, but he wasn’t upset at the prospect of going to toe-to-toe with a moggy in his latest movie. Even though he knew full well he’d be playing second fiddle to the feline. “I accepted that fact early on,” says the actor, laughing. “You knew all eyes would be on the little guy on your shoulder.” The ‘little guy’ in question is Bob, a beautiful ginger tom, who James Bowen, his owner and great friend, found injured and prowling the hallway of his sheltered accommodation back in 2007. At that point, Bowen was homeless and had spent a decade living on the streets and in temporary accommodation, but had just embarked on a drugs programme and was trying to turn his life around. Although struggling himself, he couldn’t turn his back on Bob and, after helping him heal, the pair became inseparable. They were a regular sight on the streets of London, where Bowen busked and sold The Big Issue. Bob would often sit on James’ shoulders - hence Treadaway’s earlier reference - and the pair made for quite an eye-catching sight. The unlikely partnership attracted the interest of newspapers and garnered a huge online following, as well as the attention of a literary agent, and in 2012, their story, A Street Cat Named Bob, was published. To date, it’s sold five million copies worldwide and spent almost 80 weeks at the top of the Sunday Times’ bestseller list. A second book, The World According To Bob, followed in 2013. Now the film, with Treadaway in the role of Bowen and Bob as himself (except when stunt stand-ins were required) arrives on the big screen. For all Bob’s star charisma, it’s Treadaway, 32, who carries the film, and appears in every scene. It was an intense experience. “But I like that,” says the softly-spoken actor, wearing dark trousers and a short-sleeved shirt, his hair pushed back in a quiff above huge pale blue eyes. “It’s good being in the thick of things, and if you are in every scene, every day, you just give yourself over to it. You never really have any time off, but that’s fine, it’s the same as every member of the crew.” The film’s producer, Adam Rolston, thought of Treadaway for the role after seeing his performance in the National Theatre’s production of The Curious Incident Of The Dog In The Night-Time, which earned him the aforementioned Olivier Award. “Roger [Spottiswoode, the director] and I had both seen him at the National. He was 29 at the time, but he convinces you he was this 13-year-old autistic boy,” recalls Rolston. “And when we wanted someone to play James, we knew we needed someone who could really go at it and who the audience would believe in the role. Luke is a very good method actor and he loved the script.” For Treadaway, whose twin brother is Penny Dreadful actor Harry, one of the highlights of shooting was the night shoots for scenes at the beginning of the film. James is seen walking around the capital looking for places to sleep and asking strangers for money. “A lot of the time, they [the crew] would be down the street with a long lens and filming me going up to [real] people on the street, and them not knowing what was going on,” explains the actor. “And that was good because you felt like you were in that world, privately doing it.” It was an eye-opening experience too. “There are so many people that are homeless, and there are so many reasons people fall into that situation,” he says. “It’s very easy for people to see one homeless person sit on the street and think they’re all falling into the same category, and there is, as this story shows really well, I think, a human being on every street. “It’s someone who has a past and a family and a life, and they’re just trying to do the best they can to get by. And when you couple that with addiction and other issues, it’s a really hard place to be.” Like so many people, Treadaway found the story incredibly touching. “It’s got a real purity to it,” he observes. “James and Bob beautifully balance each other in their worlds. They’re both incredibly vulnerable but they come together and help each other. There’s a transformation of fortunes. Their lives become so much happier once they meet.” It’s not the first time he’s played a real-life person - earlier this year, he appeared as late snooker ace Alex Higgins in the BBC drama The Rack Pack - but he stresses that playing someone who’s actually standing in front of you is “surreal”. “James was brought in a lot to help Bob, and it was amazing to have the person you’re playing right there for you. I’ve played ‘real’ before but not when they’re alive and on set, passing their cat from their shoulders to yours.” He also had his long-term girlfriend Ruta Gedmintas, 33, close-by, as she plays James’ neighbour Betty. It’s the third time they’ve worked together since meeting on 2011’s You Instead. “Their relationship never becomes a fully romantic thing,” notes Treadaway. “It’s a deep friendship, so maybe that made it easier in a way, because it’s not like we were trying to recreate a romantic relationship on screen.” Born in Devon, Treadaway’s father was an architect, his mother a primary school teacher, and he formed a band with Harry while still at secondary school. They both joined the National Youth Theatre, and even performed together as conjoined twins in the 2005 film Brothers Of The Head. Treadaway graduated from the London Academy of Music and Dramatic Art the following year, and has since appeared in 2007’s Clapham Junction, then Clash Of The Titans, Attack The Block, Angelina Jolie’s 2014 film Unbroken and the Sky Atlantic’s Fortitude (a second series is set to air in January). Before then, there’s Ethel & Ernest, an animated feature version of Raymond Briggs’ 1998 graphic novel, which is in cinemas now and will be shown on BBC One over the festive period. Treadaway describes it “an honour” to voice the young Briggs in the true story of Raymond’s parents, Ethel and Ernest (voiced by Jim Broadbent and Brenda Blethyn). They’re two ordinary Londoners living through a period of extraordinary events and immense social change, starting with their courtship in the Twenties through to their deaths in the early-Seventies. “I loved The Snowman and also Fungus The Bogeyman growing up,” he says. “Raymond has written this love letter to his parents and it just seemed like a beautiful story. It’s poignant and very sweet, definitely a tear-jerker.” The New Year will mark another project, but the rising star won’t divulge what it is just yet. Could it be something on stage? Treadaway laughs. “It might be,” he teases. A Street Cat Named Bob is out now