Colin Firth: My toughest role ever     Colin Firth is one of Britain's most dashing actors. But now he faces a new challenge: fighting for the world's poorest coffee farmers. He talks to Marina Cantacuzino

How do you tell consumers that their cappuccinos are driving someone somewhere deeper into poverty? How do you kick down the doors of the big coffee roasters until they're shamed into trading fairly? And how do you use celebrity to make a noise without trivialising the issue? These are just some of the dilemmas facing Colin Firth since he took on the role earlier this year as a director of Progreso—a new coffee chain whose appearance on our high streets may finally provoke Starbucks and its competitors to recognise the humanitarian crisis that lies behind the coffee they sell.

The vision for Progreso is surprisingly subversive—a global chain that offers individuality to the customer without pushing the brand, a business that pumps any value added back into the hands of producers. Giving the coffee growers of Honduras, Ethiopia and Indonesia a percentage of the business has never been done before on our high streets. Nor has appointing as a board member a respected big-name actor, albeit one still best known, a decade on, for his sodden exit from a pond as Mr Darcy in the BBC adaptation of Pride and Prejudice—a part that earnt him the epithet "the male Ursula Andress". Firth's only credential is his burning desire for change.

If there's one key thing he's learnt, he says, it's that the coffee market fails the poor. It's a shameful story of complacent governments, bullying multinationals and millions of coffee farmers around the world facing economic ruin. Few of life's little luxuries can leave such a bitter taste in your mouth—and there seems little prospect of recent events at Gleneagles making much immediate difference.

Firth's position on the board, which until now has been deliberately underplayed by star, chain and part-owners Oxfam alike, shows a level of commitment rare among celebrities, whose endorsement is sought like gold dust by charities; it's also an indication of just how seriously he takes his new role. This is not a gimmick: Firth has been to Ethiopia to see Progreso's coffee producers at work, visited Glasgow where the roasters Matthew Algie operate, and plans to roll up his sleeves and get his hands dirty too. He has already had his health and safety training and taken his turn behind the counter as a barista. "Having Mr Darcy serve the coffee is a practical way of using my profile without giving everyone earache," he says. Indeed, when he turned up for work at Progreso's Portobello Road branch last month, it seems that customers took it fairly in their stride. "People seemed to think there was nothing more normal than having me serve their cappuccinos and espressos," says Firth, and he promises to do it again.

He has been back from Ethiopia for a few days when we arrange to meet at the café. It's here, on what he calls "home turf", that he likes to hold his London meetings. Although Ethiopia has evidently made a powerful impact on him, he's only too aware that the world doesn't need to hear about yet another celebrity in Africa, especially after Live8. "If you're going to sustain commitment to any of this," he says, "there comes a point you can't feed off the buzz. Even being horrified is a buzz. You've got to get involved on an ordinary everyday basis."

Progreso looks much like any other slick multinational coffee chain, but here only fair-trade coffee is on sale. By cutting out the middlemen, coffee farmers in the developing world get a fairer price, while consumers know that, unlike at Starbucks, every cup guarantees a fairer deal for the farmer. Wyndham James, Progreso's chairman and formerly Oxfam's trading director, explains. "Our motto is sin café no hai mañana," he says, "which has two meanings in Spanish—'without coffee, mornings are no good', and, 'without coffee, there is no future'. That is the story behind coffee which Progreso wants consumers to understand and care about."

James is struck by Firth's sincerity and commitment. "He wants to work in something that makes a real difference," he says. But, quite apart from being a dedicated board member, James knows that Firth is a powerful draw to punters. On the day we meet, there is a gentle buzz around him as he takes his place in the line for a coffee.

That should come as no surprise. Firth has achieved a reputation—unwarranted, he always maintains—as one of the nation's most eligible bits of posh, a dashing-but-stoical ladykiller, after starring in Fever Pitch, Bridget Jones's Diary, parts 1 and 2, and Love Actually.

We start by talking about his trip with Oxfam to Ethiopia—a nation whose future is tied up in coffee. Witnessing the gross power imbalance between the penniless farmers and the profiting roasters was the start of what he calls "a very sobering education". "I'd read all the reports, done my homework, digested the facts," says Firth, "but actually meeting people whose dream is simply to earn enough to buy a tin roof or send their kids to school, makes it real. You're faced with emotional implications, the sheer and simple unfairness of it all."

Ever since agreeing to support Oxfam's Make Trade Fair campaign two years ago, Firth has immersed himself in the subject, invested a lump sum to set up Progreso and even bought shares for the coffee producers. Earlier this year in Geneva, he personally lobbied the World Trade Organisation director general Supachai Panitchpakdi, about Oxfam's campaign, and at a photo-call handed over their Big Noise global petition with seven million signatures. The Big Noise aims to put pressure on the big four roasters (Kraft, Sara Lee, Proctor & Gamble and Nestlé), whose failure to embrace fair-trade standards fans the flames of global poverty by creaming off profits and allowing producers to go to the wall. Back home, Firth endeavours to buy or drink only fair-trade coffee, and the message is getting through to the rest of the population—certified fair-trade coffee is now the fastest growing segment of the UK coffee market.

When Oxfam first approached Firth (at a time when the coffee prices had plummeted to an all-time low) he was reticent to become yet another celeb banging on about yet another cause: he knows it can backfire badly on both charity and star. Before now his approach to activism was radical but low-key. As a long-time supporter of Amnesty and Greenpeace he's paid his subscriptions, written letters, and been on protest marches. What changed?

"I was beginning to think I was banging my head against a brick wall and, by the time Oxfam approached me, I was wondering if perhaps, since I'm accorded a voice because of the celebrity factor, I should start to use it," he says. "But it's a great responsibility. There are so many more qualified voices than mine who don't have a chance of getting heard. I detest the fact they have to use celebrities to do the jobs for them but if that's what it takes then that's what I'll do."

On his second day in Ethiopia, Firth came face to face with how awesome this responsibility is. While visiting the Choche co-operative in the heart of the Kaffa region, the birthplace of coffee, he is welcomed with a coffee ceremony (evidence that the golden bean is much more than just a commodity here). "I was greeted with enormous grace and then their boss who was high in the union leadership said something that stayed with me for the rest of the trip. 'Three times we've been visited by well-meaning people,' he said, 'and nothing has changed.' It was very chastening and I came to see how close my visit was to being bogus and ineffectual. I knew I had to have something to say for myself or I'd just be another disaster tourist. There was no point in giving empty reassurances, so I told him I couldn't promise anything in terms of change, but that it might be in my power to get his voice heard. I asked him what he wanted to tell the consumer."

What Firth heard from the leader of the Coche Co-op, and then again and again from all the coffee farmers he met, was not an account of extreme hardship—although there was plenty of evidence of that—but a plea for a fair price for the region's top-quality arabica coffee. "The people are so emotionally bound up with the coffee. Their pleading was not on the basis of poverty but of quality. 'Give us a fair price, and we'll grow coffee on every last square centimetre of land,' they were saying."

You sense Firth's uneasiness at having discovered such beauty amid such deprivation. "We arrived in Addis Ababa and everything felt so raw and new," he says. "This feeling just grew with all of us as we fell in love with the place. It's so troubled as a country but the people we met were friendly and eloquent, which made me feel even more useless. No one projected misery or despondency—far less than on Oxford Street, actually. I met the owner of a little wooden hut with 'Art Gallery' written in crude paint strokes. He showed us his plans to build a million-pound hotel looking down over Addis. It struck me as a remarkable that a man who was lucky to have enough to get him to the end of day still had this kind of dream."

Since Firth's return from Ethiopia, the one thing that keeps nagging at him is that we are all compliant because we are all consumers. "The farmer at the end of the chain isn't asking for charity, he's just asking for a fair price," he explains. "Whenever we told Ethiopians that the price of a cup of coffee on the high-street is as much as £2.75, there was this incredulous laughter and then they shook their heads with worldly resignation. It takes 24 beans to make a cup of coffee and yet in a bad year the producer is selling a kilo of beans for just 5p. So who is making the profit? Not the farmer."

The problem is that, in the developing world, those who depend on farming to survive are suffering because trade rules are rigged against them. The solution is simple, according to Wyndham James. "The major roasters need to commit to help solve the crisis by stopping exploiting their position in the supply chain," he says. "They should guarantee a decent price to producers, they should buy more fair-trade coffee and should improve the quality of all the coffee they buy."

It sounds simple but James, like Firth, Oxfam and the farmers themselves, knows there is little chance of the roasters doing this unless pressure is put on them by governments. For this reason, Firth is now determined to use his fame to give a voice to those who don't have one. He's also determined that in three years there will be not two, but 20 Progreso outlets in the UK.

Sitting on the Progreso board is clearly one of his main priorities these days, even if regular attendance can't be guaranteed around his filming schedule. "I can't apportion time evenly, not even to my children," he says, "but if I'm away for six months the board meets without me, the coffee shops continue to trade, and from wherever I am I can continue to spread the word."

After spending several hours with Firth, talking intensely about Progreso, Oxfam and the coffee crisis, he is clearly in this for the long haul: his reticence is a reflection of his integrity, his passion, a conviction that Progreso and the issue on which it was founded has to be taken seriously.

If you want to help make trade fair, sign The Big Noise petition at www.maketradefair.com