Actor Matt Damon returns as a troubled former CIA assassin in the latest edition of the hit 'Bourne' movie series this month, reprising a role he says was physically tough to get ready for over a decade and a half since he first took it on. 'Jason Bourne' - the fifth installment of the franchise - hits movie theaters on July 27, starring Damon as a conflicted, restless hero who resurfaces at the Greek-Macedonian border a decade after going off the grid. At the movie's European premiere in London, Damon said it was a 'lot of fun' to be back in Bourne's shoes as he returned to work with familiar faces. But physically - preparing for a movie that features intense fight scenes and a major car chase - was challenging, the actor said. 'It was hard to get ready for it, much harder than when I was 29 - I'm 45 now, so it's whole different animal,' Damon, who sat out the fourth movie in the series, told Reuters on the red carpet. 'But you know, that's a good problem to have.' Asked who would win a tussle between Bourne and another legendary cinematic spy, James Bond, Damon was non-committal. But he had little doubt about who he would back as the next actor to play the MI6 spy: British actor Idris Elba. 'I like Idris - yeah, I think he's brilliant,' said Damon. 'I'll watch him in anything and he makes everything he's in better. He would make that franchise better.' In the latest Bourne edition - based on the novels by Robert Ludlum - co-star Julia Stiles returns as fellow operative 'Nicky Parsons' while Alicia Vikander, a longtime 'Bourne' fan herself, debuts as a prodigy hacker in the CIA director's team. 'The Bourne franchise was one of my absolute favorites - I'm a big fan,' Vikander, dressed in a silver sequined dress, gushed on the red carpet. 'It was a real pinch-me moment when I actually saw myself, saw the film for the first time a week ago and I was like 'Oh my God, I actually got to be in one of them!''