Blame the soaking wet shirt. When Colin Firth emerged dripping wet from a lake as Mr Darcy in the 1995 BBC version of Pride and Prejudice, the nation's women collectively swooned.
He hasn't been able to live it down since – not even when Matthew Macfadyen took on the role in the 2005 film by Joe Wright. "I was hoping that would bury it at a crossroads at midnight with a stake through it's heart but it didn't quite do that," he jokes. "It's hard to associate one's self with that after more than 12 years." Needless to say, everyone else still does.
Rarely has a one-off TV role cast such a shadow over an actor's career. Subsequently finding success in Love Actually and Bridget Jones' Diary, Firth is evidently not above a bit of self-mockery. His recent appearance as a government minister in the St Trinians remake saw him replicate his most famous scene after landing in a pond.
You might think Firth has given in to the fact that the industry loves to cast him as the affable English romantic lead. This year alone has seen him play to type in The Accidental Husband, as a New York-based publisher in love with Uma Thurman's talk-show host.
Firth denies, however, that he's done too many romantic comedies. "They just tend to be higher profile," he reasons. "People just remember Love Actually or Bridget."
To be fair, the 47-year-old Firth has tried to vary his career. Over the past four years alone, he's played a grief-stricken artist in Trauma, a sexed-up 1950s comic in Where The Truth Lies, a roman soldier in The Last Legion and a writer with daddy issues in the adaptation of Blake Morrison's And When Did You Last See Your Father? Not that it's helped.
Now, every time he does something that doesn't involve him playing posh male totty, he gets asked if it's a departure. "I'm being typecast in departures," he sighs. All he wants to do is mix it up. "I'm not looking to put on a different frock and change my walk all the time. I'm just going with what appeals to me on myown terms."
Watch the famous Pride and Prejudice 'lake scene'
Still, there's no way around it: his latest film is something of a, well, departure. He co-stars in Mamma Mia! – the film adaptation of the stage musical smash set to Abba songs. It tells the story of an 18-year-old bride (Amanda Seyfried) desperate to discover the identity of her real father on her wedding day – which she attempts by inviting three past suitors of her mother (Meryl Streep) to the occasion. Firth plays Harry Bright, one of the trio of possible paters along with Pierce Brosnan and Stellan Skarsgård.
Mamma Mia! is such a sing-a-long experience, even non-Abba fans will get a kick, Firth promises. "Even if you loathe Abba, there's a kind of enjoyment in the recognition in the songs. They're very good songs – you realise why they've survived. Even for a silly girl's-night-out-karaoke way of getting people on their feet, they've got the power to do that."
Firth is not entirely alien to singing – he sung vocals in "a ropey schoolboy band" when he was 11 – but so far, as Firth puts it, "I haven't been forced to do the kind of singing where my voice is required to be extraordinary". Yet in many ways this is the point of Mamma Mia! "If they'd wanted Broadway level dancers and singers they would've cast people like John Travolta," he argues. "They didn't: it's myself, Pierce Brosnan and Stellan Skarsgård."
Still, the sight of Firth whooping it up by the Aegean Sea is just what makes us warm to him. As an actor, Firth's always been game, willing to try anything once. Strangely, in person, he doesn't come across as so daring. He's just what you'd expect: reserved, quiet, distant, defiantly English and rather preppy-looking. Today, he's wearing a white shirt, loafers and slacks, as if he's just hurriedly changed out of his suit for a weekend in the country.
Nevertheless, given three of his four grandparents were Methodist missionaries, Firth could've been far more pious than he is. His background was built for the peripatetic nature of acting. Born in Hampshire, he spent his early years in Nigeria before returning to England when he was five to attend schools in Bath and Essex. He was not a fan of learning. "I was a schoolboy and schoolboys don't like school," he says. although he was geared up for university by his father, he got distracted, he says. "I was not disciplined enough for it." Instead, he veered off towards acting, studying at the Drama Centre in London's Chalk Farm.
Firth's first professional role was as Bennet in the West End production of Another Country, which led him to being cast as Tommy Judd in the 1984 movie version. From there, he played a soldier in the BBC's Falklands war drama Tumbledown and, a year later, the title role in Milos Foreman's 1989 film Valmont. Still, Firth didn't dent the A-list. "I have this weird thing where I keep getting discovered," he says. "Another Country was a break for me, then Tumbledown was another break. Everyone talked about the fact that nobody knew me until then, then Darcy came along and the same was said again. Then Bridget Jones – and still no-one knew me."
It's hardly a problem anymore. Later in the year, Firth can be seen in Helen Hunt's directorial debut, Then She Found Me, in which he plays "a bloke called Frank", a single father whose child is taught by Hunt's character. "It's about slightly dysfunctional middle-aged people." It's hardly a stretch for Firth, who seems to just play a more dramatic version of his rom-com persona. Just for good measure, he recently completed Easy Virtue, an adaptation of the Noel Coward play, opposite Kristin Scott-Thomas, and there's talk of him playing in a new version of David Copperfield.
Firth has recently completed the new Michael Winterbottom film, Genova. He plays a father who moves his two daughters to Italy after the death of their mother in a car accident. "It's a different area emotionally from anything else Michael's done," says Firth, suddenly lighting up. "It's a different tone, and he seems to be endlessly curious. He's got no snobbery. He would do exactly what fascinated him. He's one of the few people I can honestly say that I was dying to work with, and that's not just the usual spiel. I think everybody would be interested in working with Michael."
Also a father, Firth has been married for 11 years to Livia Giuggioli, whom he met on the set of a 1996 TV version of Nostromo, where she was a production assistant. He calls her rather formidable. "She's bright, ruthless and efficient, knows me too well and is always a step ahead." They have two children, seven-year-old Luca and four-year-old Mateo (Firth also has an 18-year-old son, William Joseph, from a previous relationship with the actress Meg Tilly). He gives the impression that his career is a distant second to his home-life. "The only reasons I worry about the next job are for the family now because I've got dependants," he says. "I'm ambivalent now about whether I want to work or not. I just want to be paid."
'Mamma Mia!' is showing now.