Colin Firth says the secret to a happy marriage is treating it like a "marathon".

The 50-year-old actor is married to Italian film producer-and-director Livia Giuggioli and he insists their 15-year relationship is still strong because they always make time for one another.

Colin - who has two sons, nine-year-old Luca and Matteo, seven, with Livia - said: "You know, we've made it 15 years together. I think that's pretty good going, by Hollywood standards. And it's going to go on forever. You just you 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."

Although 'The King's Speech' star has achieved sex symbol status through his roles in movies such as 'Pride And Prejudice' and 'Bridget Jones's Diary', he insists he ignores the attention he gets from women.

In an interview on 'Piers Morgan Tonight', he added: "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."