Gerard Butler is starting to feel the effects of his long career as an action man, and as his new film Angel Has Fallen is released in cinemas, he tells Laura Harding how he gets through the gruelling days.

Gerard Butler is starting to feel his age. The Scot will turn 50 in November, but jokingly flinches when I refer to his upcoming landmark birthday.

"Let's not talk about that," he says with a laugh. "Everybody has to be 21 sometime."

But it's no surprise the Paisley-born star is feeling the effects of his gruelling action films, even as he sits back easily in an armchair, a lock of hair curling on his forehead.

There has been a long list of ass-kicking or battle-hardened characters, each as hard-wearing as the last.

This includes 300, RocknRolla, Law Abiding Citizen, Den Of Thieves and Olympus Has Fallen, its sequel London Has Fallen, and now its latest follow-up, Angel Has Fallen.

It finds Butler's secret service agent Mike Banning also dealing with the physical consequences of a tough job.

"In some ways, this feels like my story, you know?" he says. "You make these action movies and it does take a lot out of you."

"Every time you start one, you are like, 'Oh my god, how am I going to get through this?' Especially me, I feel like I give probably too much sometimes.

"I finish a scene and go, 'Did I need to go that hard? Did I need to give that?'

"You don't often notice it then because the adrenaline is going, but the next day when you wake up and you're like, 'OK, what did I do? That was stupid!'

"I have definitely been feeling it, but I love that part of the story.

"It's just life: What does your career take out of you? What are the things that you have to sacrifice and cover for to make it through anything? But you've still got to turn up and do the job.

"I do find all these movies relentless. You always seem to be finishing off one five-day action scene, then you have two days of bits of dialogue and then back into another six-day action sequence.

"But that is part of it, that is what the character is going through, that is what you're going through as an actor, and that is what's fun about the movie."

While the first two films have revolved around terrorist attacks on the White House and London respectively, Angel Has Fallen finds Banning with US President Allan Trumbull, played by Morgan Freeman, when there is an assassination attempt and all the other Secret Service agents are killed.

Banning is immediately the prime suspect and must go on the run while he tries to track down the real threat, turning to his estranged father, played by Nick Nolte, for help.

So much action inevitably means lots of violence and lots of guns.

In today's climate, is Butler, who is also a producer on the film, mindful of that?

"We are always talking about it," he says.

"You can't make these movies without guns, but I don't think there is a ridiculous use of guns in these movies.

"There are actually more explosions than guns, but there are also fists, there are elbows, there are knives. It's an action movie, so we are not going to make it with squirty guns or custard pies like... what was that movie?"

Bugsy Malone?

"Bugsy Malone! My favourite," he chuckles.

"We are conscious, but it can't stop you making the movie you're going to make."

And Butler wanted the film to be a character piece as much as an action film.

"We gave this film a lot more soul and depth and personal emotional journey than the other ones," he says.

"We flipped everything on its head.

"I've come to love this guy, I get him and I like him and I understand him, but we took a gamble. We said, 'We could make a third one and just make it another terrorist attack and another city, but let's not, let's trust that an audience will really buy into character as well'."

That's not at the expense of the high-octane action scenes audiences are expecting, he is keen to stress.

"We actually have almost twice as many action sequences in this movie as we do in London, so you get a nice mix of both.

"And you're even more in the action sequences because you're more with the character and everything that he's going through.

"In some ways, it makes it really quite relentless, but you have time to watch that relationship with his father and it's super emotional.

"You see his family and you see all the colours that are going on with this guy, who is on the run with the whole world against him."

Having 78-year-old Nolte, the star of films such as Affliction, Prince Of Tides and 48 Hrs, play his father felt particularly important.

"I have to say, that was a major coup for us and hanging out with him was extraordinary, it was just beautiful.

"Times like that I pinch myself and go, 'This is cool', and as an actor watching him perform and him being my dad, that is my favourite relationship in the movie.

"I think the audience feels it too. I watched it again last night and whenever he and I are together, you are either crying or you're laughing hysterically, it works great.

"I think we have to have our own spin-off, a kind of Hobbs and Shaw, me and Nick Nolte.

"I don't think it will be quite as sexy as The Rock and Jason Statham, but hey, we will try."

Angel Has Fallen is released in UK cinemas on Thursday, August 21. See Saturday's Herald Magazine for Paul Greenwood's review.