James McAvoy says "secrecy" is the key to his long lasting relationship.

The actor married British actress Anne-Marie Duff in 2006 and the pair mutually agreed never to discuss their relationship with the press.

James believes that they would not have lasted so long if they had published private details.

"the key to a successful marriage is secrecy at all times. Not saying anything about it in public. Keeping it as quiet as possible," he told the UK edition of Hello! magazine. "But then I'm kind of boring anyway, so who really cares about my private life?"

The star has acted in blockbusting movies such as X-Men: First Class and The Chronicles of Narnia: The Lion, the Witch and the Wardrobe.

However, James claims he doesn't earn enough for a A-List way of life.

"You can have a nice movie lifestyle if you want, but to be honest I don't earn the kind of money you need to maintain a tremendous lifestyle anyway.

The couple also have a 12-month-old son together called Brendan.

James admits that being a dad is difficult, but definitely worth it.

"I sleep a lot less, I don't drink as much and I don't work as much," he laughed. "But it's good it's changed life for the better."