Colin Firth has opened up about his relationship with wife Livia Giuggioli, saying that marriage is like a “marathon”.

“You know, we've made it 15 years together,” the actor said on Piers Morgan Tonight. “I think that's pretty good going, by Hollywood standards. And it's going to go on forever. You just navigate things on a daily basis. We are crazy about each other.

“We're very committed on a daily basis to how we deal with our family lives. But the real secret is time - we have to make sure that we spend enough time together.

“Every relationship in life you're going to have to take care of, there's a marathon factor to it.”

The 'King's Speech' actor said that he is never tempted to stray from his wife, explaining: "It does help to actually realise that however stunning the person who is, you know, fluttering eyelashes at you is, she doesn't do anything to match up to your wife.

“Maybe it's shallow of me to have a wife that's so beautiful but it actually makes things easier. To me she's the most beautiful woman in the world.”