"I've said it before, and it's only getting more and more accurate as cast members keep joining, there has never been an ensemble like this in cinematic history," says Marvel president Kevin Feige, who produces the films and had to make the decision about where to draw the lines as the Avengers divided into two warring teams. "it was a chessboard - who sides with whom."

Chris Evans stars as Captain America

As the title suggests, Chris Evans' Steve Rogers is the pivotal character, and he says that filming these movies is "like it's summer camp", as the actors rarely fall out over anything.

To which Robert Downey Jr. quickly replies with a laugh, "Speak for yourself! My son has started wearing Captain America pyjamas, and that breeds a resentment!"

Of the central conflict over whether the Avengers should be held legally accountable for their actions, Evans confesses that "in the real world I'd be Team Iron Man. There'd have to be oversight." But he understands Rogers' desire to help people without first going through a committee.

He also says that it's the mixture of physicality and drama that keeps him interested in playing the character. "The action is exhausting and physically demanding, but I think what is harder is in terms of approach as an actor are the emotional scenes," Evans says. "There is a much greater personal responsibility in those scenes. The emotional moments are up to you."

Although he also notes that some of the bigger action moments can take their toll. Of a memorable scene in which he holds onto a helicopter wearing a short-sleeved shirt so his rippling biceps are on full display, Evans says, "Yes, that was me! But I genuinely did mess up something in my arm doing it. It's a very unnatural position to be in, but you're trying to look good! We shoot those scenes early on because I lose weight the longer I wear the suit."

And he has no intention of stopping quite yet. "I say, let's keep going, let's let the wave get bigger and bigger," Evans says. "It's not like they're making bad movies; you can put them in this superhero box, but they're good movies. And the battle in this one leaves the Marvel universe in a bit of disarray, which will be great for future films."

Watch the trailer for Captain America: Civil War: