“I mean Cary Grant is the GOAT [greatest of all time], the style icon of the last century and probably this one,” the 48-year-old says. He notes that designer Tom Ford, whose career was arguably made possible by the seminal grey flannel suit Grant sports in the film, even makes a range of sunglasses called “Cary”.

“There would be no Bond films or Bourne films without the Hitchcock movies that Cary epitomised, and he’s still influencing fashion and acting techniques today.”

Rather than give the audience a “budget Cary”, Campbell instead focused on the Thornhill character who emerges from the page in Carolyn Burns’ stage adaptation of Ernest Lehman’s original screenplay.

“There is a bit of Cary in there at the start. There’s a musicality in the way these classic Hollywood actors spoke that makes me feel at home, even if I’m not belting out a top G,” says Campbell, a decorated veteran of jukebox musicals celebrating the likes of Johnny O’Keefe and Bobby Darin, whose last non-singing role was an off-Broadway season of the play Love! Valour! Compassion! in 1997.

Campbell admits to imagining Thornhill as the type of guy who, like many men in the late 1950s, went to Cary Grant films and tried to emulate his understated cool.

“But then later on, when Roger’s back’s against the wall, I’ve tried to bring out the brawling New Yorker in him,” he says.

Campbell also admits to feeling like he’s been in a brawl as the curtain closes on North By Northwest each night.

Director Simon Phillips has moved mountains, literally, to recreate North By Northwest’s lightning-fast plot and epic action sequences on a theatre stage, including the crop-duster and Mount Rushmore set pieces.

“We’re quite a mature company, and Simon’s got us doing a whole lot of climbing and jumping and moving props around. It’s thrilling but it’s tiring,” says Campbell, who backs up each morning as the host of Today Extra on Nine (owner of this masthead).

“Me and my old mate Bert LaBonte, who plays the bad guy, used to talk and dream about doing productions like this. Now that we are, the first thing we ask each other is how our knees and lower backs are going.”

North By Northwest is at Sydney Lyric until April 3.