Princes William and Harry attend 'Star Wars' London premiere

Britain's Prince William (left) and Prince Harry are rumoured to have cameo roles in "The Last Jedi". (AFP/Eddie MULHOLLAND)

The British royals walked the red carpet dressed in tuxedos for the screening at London's Royal Albert Hall, where they were greeted by the rolling droid character BB-8 who dutifully bowed to the princes.

The two reportedly have cameo roles as stormtroopers in the film, after visiting the set in April 2016 when they were rumoured to have shot the scene.

William and Harry - who recently announced his engagement to US actress Meghan Markle - also met the cast of "The Last Jedi" and were presented with stormtrooper helmets.

Filmed at Pinewood Studios near London and on the west coast of Ireland, "The Last Jedi" is the eighth film in the space series and runs to a lengthy 153 minutes.

Mark Hamill, who plays Luke Skywalker in the films, said the longevity of "Star Wars" had seen his character make way for new stars.

"It's like a bunch of kids rifling through my old toy box, playing with my toys... I love it!" he told AFP at the premiere.

Despite 40 years passing since the intergalactic saga first hit cinemas, the cast members of Rian Johnson's "Last Jedi" are convinced it still has contemporary relevance.

"I think it really deals with issues the world is facing at the moment, about politics which splits people apart and the spark of hope which is going to bring people back together again," Andy Serkis, who stars as Supreme Leader Snoke, told AFP.

Lupita Nyong'o, who plays the motion-captured character Maz Kanata, said the film was also important as a form of escapism.

"I think the importance of fantasy is that it allows us to first of all, escape from the world we're in for a second and it brings us all together and unifies us in a way, on a subject, in a way that other things don't," she said.

"And for a moment we get to forget our own worries and worry about the galaxy far, far away."