Colin Firth will forever be remembered as the perfect Mr Darcy – rich, handsome, chivalrous and, as many women will recall, very fetching in a dripping wet shirt.

So what does he drive? A classic Jaguar perhaps, or maybe something discreet from Bentley? No, until a couple of years ago at least, Firth, 46, was to be found behind the wheel of a dependable Morris Minor. He was still happily driving his very first car, bought in his twenties for £2,000. It might not have won over Bridget Jones, but it was good enough for him.

“I am not a Bentley sort of chap,” he confides, fresh from a film screening in Cannes, where the streets are lined with some of the sleekest, most expensive cars in the world.

The key to understanding Firth is to recall the sort of roles he took before the BBC adaptation of Jane Austen’s Pride and Prejudice turned him into a sex symbol and national treasure in 1995.

He first made his mark in 1984 in the award-winning stage production of Another Country, then played alongside Kenneth Branagh in 1987 as a stuttering first world war soldier in the film version of JL Carr’s novel A Month in the Country. He then sealed his reputation as an actor with a gripping performance as Falklands officer Robert Lawrence in the powerful 1988 television film Tumbledown.

But after Darcy just about anything became possible, whether the Arsenal fanatic in Fever Pitch, the ridiculous Lord Wessex in Shakespeare in Love or winning over Bridget Jones in two box office hits.

“I was working at edgy, serious stuff for years,” he says, “but a lot of it wasn’t seen. I remember doing Master of the Moor, playing a character who chopped people’s heads off.

“Yet it is things like Bridget Jones which stick to your skin, and I stepped on a timebomb with Mr Darcy in Pride and Prejudice.”

It was a life-changing experience for Firth, bringing instant fame and an adoring female fan base. Yet he was advised not to take on the role of the brooding Darcy. “I could not have been more wrong for it,” he says. “I am totally unlike Mr Darcy. I talk like a blue streak, I don’t own a horse or acres of property. I’m a secondary-modern schoolkid with no links to nobility. Yet I played this taciturn, dark, sexy guy and everyone remembers it.”

Rather than riding manfully across his sweeping country estate on his trusty steed, Firth is now the rather sheepish owner of a petrol-electric hybrid Toyota Prius. “I don’t want to come across as worthy,” he says apologetically, “but I have never been excited by big, high-powered cars. They look okay, I suppose, but they are just not for me.”

Firth was on the verge of buying a humble Honda Civic hybrid before opting for Hollywood’s latest fad car for A-listers keen to promote their green credentials. Despite his protestations about not wanting to appear worthy, he has a reputation as a celebrity do-gooder. He recently threw his weight behind a campaign to help Congolese asylum seekers who were threatened with deportation from the UK and has also spoken out in favour of fair trade.

His former co-star Rupert Everett has described him as “boring” and a “ghastly guitar-playing redbrick socialist who was going to give his first half-million to charity”. The pair fell out in 1984 while performing in Another Country, sealed their mutual antipathy during filming for The Importance of Being Earnest in 2002, but recently made up on the set of the new St Trinian’s film, to be released in December, in which Firth plays the education minister Geoffrey Thwaites.

His latest project is a film made with his wife Livia. She is producer and he executive producer of In Prison My Whole Life, a documentary recounting the story of the political activist Mumia Abu-Jamal, who was sentenced to death in America in 1982 for killing a police officer. The verdict was overturned in 2001 because of errors made in the original hearing.

“It is very politically sensitive and has to be launched in the right way,” says Firth. “Did he really do it? I honestly don’t know. My wife is the producer and the real powerhouse behind the film, which is wonderful.”

Firth’s parents both grew up in India, where his grandparents were involved in missionary work, and his mother became a lecturer there in comparative religion. He feels uneasy with the trappings of fame, be they flash cars, Alist parties or sycophantic flunkies.

“Once you’re a celebrity, it seems you don’t play by the same rules as the rest of society,” he says. “People will be nice to you all day long for no other reason than they’ve seen you in movies.

“So you need to find something other than your celebrity to give you strength and your life some meaning. Otherwise you can end up in rehab – or worse.

“A lot of people fall apart because they get too much of it. When I look back I realise that those are the people who had nothing more than celebrity to keep them going.”

Although it’s hard to imagine Firth ever ending up in a Lindsay Lohan-style dash to rehab, he claims it is his home life that has kept his feet firmly on the ground.

He says the new Prius will be ideal for his young family. He and Livia were married in 1997 and now divide their lives between Italy and London with their two boys – Luca, 6, and Mateo, 3. Firth also has a 16-year-old son, William, from a previous relationship with Meg Tilly, the American actress he met when they co-starred in Valmont in 1989.

“My family, my wife and children and a handful of very close friends are what have kept me going,” he says.

“If I get less money and less fame than some people, it just does not matter to me. I have never been an enormous star. The tragedy can be that when you have had a career which has soared, there is nowhere to go but to fall.”

On his CD changer

It varies, but I’ve just been listening to Sky Blue Sky – the new album by Wilco which is great

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