Sex on legs! Me?   He may be the world's most romantic leading man but Colin Firth draws the line at getting his pins out for his latest Roman epic role

He's one of the sexiest men on legs after his starring role as Mr Darcy in Pride and Prejudice, but it's exactly those legs that are worrying Colin Firth. Famed and adored for playing romantic dashing leads and no stranger to dressing up for a part, movie hunk Firth was worried his latest role might make him more comedy star than swoon material.

Off to Tunisia and Slovakia to film The Last Legion, an epic drama set during the end of the Roman Empire, the 45-year-old plays a seasoned Roman general guarding the boy emperor from ferocious barbarians.

But it's the costumes—and his legs—which are playing on his mind.

He said: "Whether you have the build or not, you can be killed in a costume.

"Russell Crowe didn't look ridiculous, but even if you have the most incredible physique there is still the danger of looking comical flaunting it in a skirt.

"You might become some kind of cheesy erotic fantasy."

And he added, clearly concerned about how he might look: "It is dangerous if you have beautiful legs and dangerous if you have legs like pipe cleaners. I can leave you to guess what applies to me."

Luckily producers have set The Last Legion, which also stars fellow Scots Peter Mullan, James Cosmo and John Hannah, in a period where fashions of the day mean he is covered up.

Colin said: "I thank my blessings that the film takes place at a time when they were out of mini skirts and wearing slightly more dignified apparel.

"I have done masses of the more balletic style of sword fighting, but this type of combat is more cut and thrust."

Colin is relieved he is more covered up because he is only too aware that even some of the hunkiest stars of Hollywood, like Brad Pitt in Troy, have some difficulties with that sort of outfit.The Roman adventure is an interesting change of direction for Colin, who has earned fame and acclaim for starring in a string of hit romantic comedies.

These include the two Bridget Jones movies, Oscar-winner Shakespeare In Love,The Importance Of Being Earnest, Love Actually and his current success, kids' film Nanny McPhee.

But now he's contemplating a role that would shatter his romantic image—a movie titled Toyer in which he'd play a madman who lobotomises women.

He said: "I think it will upset a lot of people...understandably, it's a very upsetting script. But it may or may not happen, I'm waiting to see."

It's confounding people's expectations of him as an actor by mixing up the types of roles he takes that fills Colin with enthusiasm for his craft.

He said: "Sometimes I can't believe how ridiculous my existence is.

"I could be lobotomising women one minute and riding across the desert wielding a sword the next."

The next film that is on the way will provide another look at the edgier side of Colin's talents, because in Where The Truth Lies, Colin and Kevin Bacon play a Fifties comedy double act.

The characters are not above taking advantage of their groupies and one pivotal scene in the movie sees Colin and Kevin involved in a threesome that goes horribly wrong.

He said: "I have done stuff that is a long way from the romantic comedies I'm known for. But it is not to do with career strategies or trying to change perceptions of me, it's just what keeps me amused."

While he was filming Nanny McPhee—in which he plays the single father of seven children whose life is changed by a magical nanny played by Emma Thompson—Colin got some unexpected help as he prepared for Where The Truth Lies.

The cast of Nanny McPhee included Hollywood legend Angela Lansbury, who had met the sort of showbiz acts that Colin portrays in the movie.

He said: "So here I had someone who knew The Rat Pack and she was fantastic with her advice." Colin is married to Livia Giuggioli, with whom he has two children, four year-old Luca and Mateo, two. He also has a 15-year-old son from a relationship with American actress Meg Tilly.

No doubt it was with his younger sons in mind that he agreed to star in Nanny McPhee and experience his first big screen slapstick when he gets involved in a frantic and messy pie fight.

He said: "I can't imagine that it is ever going to happen again.

"But I realised from day one that I was going to be asked to participate in something that was very broad. It was nerve wracking because I'm not known for that."

While you can imagine the Firth children one day getting a lot of fun from seeing dad making a fool of himself in the pie fight, Colin is quite content to keep his children distanced from his career.

He said: "I'm not particularly anxious for my youngsters to see my work early on. Until they start to get really curious about it all I will leave it. It's a bit odd watching dad running around in a film."

Nevertheless he has taken a significant step towards classic family movies because Nanny McPhee is the first children's film in which Colin has starred.

He said: "If you are talking about targeting kids who are under 12, then I have never done anything in that area.

"I did What a Girl Wants, but that was more of a teen film."

Colin got his first taste of acting in pantomime as a five-year-old doing Jack Frost, but now he's so frequently on screen that he seems to be one of our busiest actors. But he insists he's far from a workaholic.

"People think you never stop, but the reality is I have an average of two films a year.

"I used to do a lot more films back to back before I had a family of my own.They are my reason for paring it down a bit," he said, adding that he is also aware of the dangers of being too prolific.

"I think people do need a break from you. If there is a Bridget Jones film out, you are on the side of every bus.

"I get sick of being stuck in traffic in London and getting overtaken by a bus with my face on the side."

Mention of Bridget Jones caused me to ask what he reckons the chances are of a third comedy in that series, and Colin admits he has mixed views on that topic.

He feels it could be in the running if author Helen Fielding was to dream up the plot for another brilliant book that was irresistible.

Colin said: "But I wouldn't want to do a third Bridget Jones film that just went over the same ground.

"However if it was about a sad, unhealthy, bloated Darcy and Cleaver (Hugh Grant's character) as a pathetic, ageing Don Juan with a fake tan and Bridget being even more neurotic, it might be good."

#Nanny McPhee is released today and Where The Truth Lies is out on December 2