James McAvoy, star of stage and screen, has a secret anxiety. The Scottish actor has revealed to the Observer that his confidence has been dented in the past by criticism from a pair of well-known British writers, both of them behind stories he has starred in on screen. “It is not nice. I’ve had that with two writers, actually.” It happened first when he played the lead in the award-winning 2007 adaptation of Ian McEwan’s Atonement. McAvoy says the author suggested he was two slight for the role. “He said I was a bit small – because my character, Robbie, was meant to be this 6ft tanned Adonis, and I was a 25-year-old pasty Glaswegian who’s 5ft-nothing,” the actor recalled, grimacing at the memory. The incident, he adds, left him “a bit devastated”, although he admits that McEwan, one of Britain’s most successful novelists, “wasn’t disparaging. He just gave me … nothing.” On another occasion, the actor claims he was unnerved by similar comments from Zadie Smith when he was to appear in the 2002 dramatisation of her debut novel White Teeth. “She didn’t say I was bad at playing the part. She told me I was the wrong casting, because I was too little – the character should have been more overweight.” He remembers reacting with surprise. “I was like, oh, you could have said: ‘Nice job, thought you did great, I never saw him as a skinnier guy.’” And, as an actor who is known for utterly committing himself to a role, the encounters have troubled him. It has even led him to avoid meeting one of his literary heroes, Philip Pullman. McAvoy, 43, is a big admirer of His Dark Materials and has spent the past four years, on and off, appearing in instalments of Pullman’s fantasy books. McAvoy is inspired, he says, by Pullman’s central message: “The fight against oppressive moralistic institutions is something I found quite fascinating.” Yet he has “never spoken to Philip Pullman”, he admits, because he is concerned about falling short once again. The actor’s more recent concern is to avoid pouring too much energy into his career: “I don’t want to just be that guy who was Bill Murray’s character in Lost in Translation, where he’s basically not got a life because he did the movies – and he can’t remember any of the movies. And yet he’s estranged from his wife and kids.” McAvoy is a new father to a son for the second time, with his second wife, American Lisa Liberati, and now faces a choice, he admits. “Do I keep chasing, do I keep progressing, do I keep trying to climb the ladder, the mountain, all that kind of stuff? Or do I just continue to enjoy the act of acting – but taking the foot off the pedal?”