Both he and director Paul Greengrass ruled out any further films, prompting the studio to make the 2012 reboot The Bourne Legacy. A few years later, Damon and Greengrass agreed to come back. "It's a tough thing to earn an audience's trust and so we didn't just rush into it," Damon says. "We waited for 10 years or so and got a good story."

Matt Damon a the European premiere of Jason Bourne

The new film, simply titled Jason Bourne, opens with a big fistfight. "We shot that scene, that first fight, on the first day and it was like, we're doing this," Damon says. "It won't be said that we came to pick up a pay cheque. We're going to give it absolutely everything we have!"

But how difficult was it for Damon to get back into top physical shape 14 years after the first film in the series? "Oh, it was absolutely a different experience," he laughs. "Paul said early on, that Jason Bourne couldn't look like he has lived well these past 10 years. He has to look like he has suffered. And the only way to do that is to suffer."

In Damon's case, suffering meant a gruelling 10-month period of diet and intense gym sessions. "Paul really wanted me to be physically fit and lean," he says. "And it was a lot of work for me to get there! For the first Bourne movie I was 29 and I thought that was hard work getting into shape. Now I'm 45 and it's just brutal."

Damon says that he only has about 25 lines of dialogue in this new movie, noting that the character has spoken less and less on-screen. "After his girlfriend dies in the second movie, Bourne becomes a very lonely character," he says, "The screenwriter was worried that I had so few lines, but I love that."

Of course, now that he and Greengrass are back in action, questions are swirling about whether they'll make another Bourne movie together. "Paul always says that the worst time to ask that question is right after you've made one," Damon says. "My guess is it will be a while before we'd get around to doing another one. Actually, they might reboot me before I bow out."

Watch the trailer for Jason Bourne here: