Arnold Schwarzenegger returns to his most famous role in Genisys

"I'm old but not obsolete," says Arnie on reprising his role in the new Terminator movie.

Arnold Schwarzenegger in Terminator Genisys. Melinda Sue Gordon / courtesy Paramount Pictures via AP Photo

"I'm old but I'm not obsolete," Arnold Schwarzenegger says of his return as the fearsome cyborg from the future in his new movie Terminator Genisys.

The line is taken from the movie, spoken by his robotic character, but applies equally well to the 67-year-old Austrian-born Hollywood actor and former governor of California.

Schwarzenegger says he was asked to reprise his most famous role a month after finishing his seven-year stint running California in January 2011.

“I was very, very excited to ‘be back’,” he says, putting his accented emphasis on what is now his trademark phrase.

Terminator Genisys is the fifth movie in the series that launched in 1984 with Schwarzenegger playing a killer cyborg sent to slay Sarah Connor, the woman who would become mother to a future resistance leader fighting the ­machines.

Schwarzenegger (who wasn't in the last Terminator film that came out in 2009 because he was in governor mode) revisits the original 1984 time frame thanks to some movie magic.

He describes a key scene in the movie that sees him fighting the cyborg he played back in 1984, a struggle made possible by the time-travel concept of the series – and modern special effects. For the fight scene, the production hired a bodybuilder with "a Mr Universe physique" to play the younger version of Schwarzenegger, before spending a year using computer graphic overlays to make him look like the first Terminator. Schwarzenegger says his young face had to be totally recreated. Not "one single frame" was taken from the first Terminator movie, he explains, because it is owned by a different production company.

“When I saw the movie for the first time three weeks ago, I was literally blown away to see myself fighting me and to see exactly the way I looked in 1984,” Schwarzenegger says.

“I didn’t actually know when I saw the fight who I should root for.”

His appearance as a Terminator visibly three decades older shoudn’t be unconvincing for fans of the franchise, Schwarzenegger explains, because it is explained in a “very well-written” way.

He also credits modern movie magic for making it possible to continue in other action roles at an age that many men are enjoying ­retirement.

He points to next year's Conan sequel, for instance, where Schwarzenegger is reprising the title role from the first feature movie he made 35 years ago. "All of this is very unusual, because normally when you watch movies such as James Bond or Batman, they switch out the actors every five, six or 10 years."

But the former bodybuilder says: “When you have a studly body, you shouldn’t be surprised.”

Terminator Genisys reserves some surprises, not least by introducing British actress Emilia Clarke, of Game of Thrones fame, as a tough Sarah Connor – and propelling the story into near-present day.

Along the way, it blends together characters and events from the earlier movies.

Australian actor Jai Courtney plays Sarah's would-be saviour, Kyle Reese, and Terminator Genisys is directed by Alan Taylor, who recently made the Marvel blockbuster Thor: The Dark World.