The $2.5bn dollar man: Matt Damon

He is the two and a half billion dollar man. That is the total box office Matt Damon has produced for a grateful Hollywood since his career began with Good Will Hunting back in 1997. Franchises like Bourne and Ocean's Eleven, as well as critical and commercial hits The Talented Mr Ripley, Saving Private Ryan and The Departed meant that as of 2007, Forbes magazine estimated that Damon was the most dependable star in the industry, producing $29 of clear profit for every dollar the studios paid him.

Meeting him in Berlin, it's not hard to picture Damon quietly and affably working away for the good of others. Famously baby-faced for a 42-year-old, his light-up-the-room smile makes him seem even younger. He is easy to talk to, but, Jason Bourne aside, Damon would make an ideal spy in real life – his words, his appearance, don't linger in the mind. He's like an everyman who just happens to have stumbled upon movie-star status.

This conclusion though, would be an insult to Damon's obvious ability, which is on display in his latest film Promised Land, directed by Good Will Hunting's Gus Van Sant. Damon plays a corporate salesman who is trying to buy gas-drilling rights from the residents of a small town in rural America. The film centres on the topical and controversial process of fracking – the extraction of natural gas that is trapped underground.

Significantly, this was to be Damon's directorial debut, “But then my schedule got the better of me and I knew I wouldn't have time to do it,” he explains. “It nearly killed me to give it up,” he adds with a glint in his blue eyes, “especially as I had to settle for Gus Van Sant making it instead.”

Only Gus would do for Damon: this is one of the few movie scripts the actor has written since Gerry in 2002, which was also directed by Van Sant. Damon co-wrote Promised Land with John Krasinski, star of NBC's The Office, and he credits him with making it happen. “I was shooting a movie and unable to commit to much, so the entire movie was written over a series of weekends. The whip really had to be cracked on me.”

Writing remains the skill for which Damon has been most highly rewarded in Hollywood; 15 years ago he and Ben Affleck won the Best Original Screenplay Oscar for Good Will Hunting – two Boston boys hitting the big time after touting their script around town for years. Yet he is still slow to write.

“I need a writing partner,” he confesses, “Or I can't do it. I was an English major at college (Damon attended Harvard, but dropped out before graduating) and I hated the solitude of just staring at the computer screen, it drove me nuts. Creative writing is different of course from essay writing. It's more active – and when you have a partner to do it with, there's scope for improvisation and a lot more laughter. Although you sometimes have to force yourself into a cubicle and tell yourself 'I am doing this right now'. Often better writing happens by osmosis when two people hang out. Ben Affleck and I always had a blast when we wrote.”

Ben Affleck, the man who shares Damon's writing Oscar – and for many years, back in their broke days in Boston, his bank account – is still his best friend. After Affleck's success with Argo, Damon may have to join the queue of writers wanting to work with him, but he says that the pair will reunite on a script in the near future.

“My family and I are moving to LA from New York this summer, which is a really big event for us,” he says. “We've actually bought a house just down the street from Ben. We own a production company together, and we're going to rent some offices, and so yes, hopefully we'll be cooking things up together soon.”

Affleck and Damon were neighbours too as children; they grew up two blocks away from each other in Cambridge, Massachussetts. Damon lived with his university-professor mother after his parents divorced. Both classmates wanted to be in the movie industry; Damon's first break came with a single line opposite Julia Roberts in Mystic Pizza in 1989, and he left Harvard a few credits short of his degree to pursue acting. Both actors then spent years trying to get their script about a maths genius made. Good Will Hunting, Damon said modestly, “was a high-stake film and it worked out as best as it can in this business.” After its release in 1997, Damon's career went from strength to strength; Affleck sank to the depths with “Bennifer”, his relationship with Jennifer Lopez, resulting in 2003's disastrous collaboration, Gigli.

Now however, Affleck is the man of the moment, and there is joy on Damon's face as he speaks about his friend's spin back to the top of the Hollywood wheel. “I am really, really happy for him. He has taken everything on the chin over the years. Ten years ago I remember I spoke to him and he was in such a rough spot. He said to me, 'I sell magazines but not movie tickets, I am in the worst possible situation.' He really had to take himself out of the scene and I'm proud of him for turning it all around. His life has been so interesting, it's a rollercoaster.”

It's hard to imagine Damon sharing the same ride. Other than a famous guest spot in Sarah Silverman's video, “I'm fucking Matt Damon” on the Jimmy Kimmel show in 2008, his marriage has been as solid and dependable as his career. He met Argentinian Luciana Barroso in a bar in Miami in 2003 (she was the bartender) and married her in 2005; the couple have three young daughters and Barroso has another, Alexia, from a previous relationship.

Fatherhood, says Damon, “is something I've always wanted to do. Although the sleeplessness is the toughest part. Sometimes you're looking at the clock in the middle of the night and it's the time the Navy SEALS are usually sent to kill you. That's hard.” He relishes the ordinariness of domestic life, adding, “If anyone wanted to take secret photos of my life, they would be bored within a day. A few hours of me doing research or learning my lines – the press would soon go home.”

Self-deprecation is clearly Damon's style. He once quipped that his scripts were “the cast-offs from Brad Pitt and Leonardo DiCaprio”. And who else would have coped so stoically with Team America's “Matt Damon” puppet passing into popular culture as a synonym for something stupid and slow?

Niceness, argues Damon, “is not something I set out to achieve by holding myself to a certain standard of behaviour. I don't know why people like me. I'm glad they do and I'm glad they still go and see my movies.”

There is a hint of controversy over his latest film however. Promised Land has been singled out for criticism for its portrayal of fracking, unsurprisingly by supporters of the method, but also by a group of farmers living near the real-life film set in Pennsylvania. They set up a Facebook group to accuse the film-makers of having “a condescending view of farmers”.

When the film was released in the US in December 2012, the industry group Marcellus Shale Coalition was sufficiently perturbed to buy an onscreen advert to be shown in cinemas alongside the movie. So far the movie has made half of its $15m budget back – but in Europe it has been more favourably received, winning a Special Mention at the Berlin International Film Festival this year.

“I don't think it deserves this kind of withering attack,” says Damon. “There isn't a scene in the movie that I would change or do differently, but it didn't get the reception I hoped for. Sometimes people find movies later on, and I personally love it. I really don't understand the criticism that I've been hearing back.”

The film explored something which is particularly on the actor's mind, namely “the American identity, and what will be left behind for future generations? It's a heart-breaking situation in rural America at the moment. You think a recession hits a city hard? Go to the countryside.

“These small family farms are really struggling and it's very hard to see. So something like fracking comes along and offers a small farm a potential financial lifeline, but there are risks involved to their environment and which could threaten their whole way of life. I wanted to start a discussion on that, not make a judgment.”

A committed Democrat – he once called Sarah Palin “a bad Disney movie” – Damon laughs off suggestions that he might run for office one day. His concerns, he says, are that “people are actually going hungry. I would rather the public listened to politicians rather than celebrities. But sometimes politicians don't talk about these things.”

What he still really wants to do, he says, is direct – but first he has the lead in Neill Blomkamp's sci-fi epic, Elysium, which is released in August. Damon stars as Max, a Mr Ordinary with a chance of saving the planet. Ordinary, of course, is what he does best, but the real compliment may be that his character in the film is just 29 years old.

“People forget that Ben and I have been kicking around for 15 years now,” he smiles. “Apparently when Ben was shooting The Town back in Boston, he pointed out our old place to the cast, and Blake Lively says, 'You know Jason Bourne?' We're so old now that the first part of our history has been forgotten.”

'Promised Land' is released on 19 April