Idris Elba promises "classic Luther" as he drops cryptic clues about series 5

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But now he is about to plunge back into the world of John Luther as he returns to the BBC for four more episodes of the popular crime drama.

Elba wants to stay tight-lipped on the drama that made him a household name ("I can't say. I'm really sorry. I can't give you anything") – but he can't help himself from dropping a few intriguing hints. "I mean there is a lot of excitement about the characters that are in this one," he says.

Characters like enigmatic killer Alice (Ruth Wilson) or sidekick DS Emma Lane (Rose Leslie) perhaps?

"We'll have to wait and see!" Elba teases, before adding the promising remark: "There's no point trying to make something unfamiliar."

So why did he decide to put on the coat he first wore seven years ago, and return to the part of John Luther?

"Luther has never been scheduled to do it every year," he explains. "We do it whenever we want, and that's why this feels like a good time to come back; it's just because we've been away for a while.

"There is unfinished business, but there's also more Luther. There's more of that really complex character that I love to play."

Four years ago the show's creator Neil Cross sparked huge excitement amongst Luther fans when he revealed a film adaptation had been written. Since then reports of a movie appear to have gone quiet.

However, Elba's keen to revive the project – and in fact, he has a much more ambitious idea.

"It's very much in our minds, the film," he reveals. "I think it could be an amazing series of films."

Are we still talking about the same movie script Cross mentioned all those years ago? "It's taken on some different legs, but it definitely feels like it would be magnified more – open Luther in terms of what he can do, on a film scale," Elba explains.

The Hackney-born actor has had plenty of experience working on a "film scale" in the last few years, with starring roles in The Dark Tower, Star Trek Beyond, Zootopia, the Avengers and Thor movies – and now The Mountain Between Us, where he plays brain surgeon Ben Bass.

Ben finds himself stranded in the snowy mountains after a plane crash which leaves him, photojournalist Alex Martin (Winslet) and a baffled labrador as the only survivors.

Elba's character is a reserved Englishman who is reluctant to talk about his personal life, while American Alex can't help but pry. And as they struggle to work out how to survive in the freezing mountains and reach civilisation, Ben is cautious – while Alex wants to take more risks to save both their lives.

"I could relate to him being guarded," says Elba. "Personally, when someone asks me a lot of questions I'm always sort of like: 'Hm, why do you want to know that?'

"I'm growing out of that actually, because I realise that sometimes the nosy person doesn't mean that they've got anything they're going to do with the information, they're actually just trying to get you to open up a bit, which is okay. And Ben's a bit like that.

"But I think I'm actually more like the Alex character in reality. If we were stuck on a mountain, I'd say, 'Look man, we've got to get out, let's go. Let's get out of here. Let's figure it out.'"

That bolshyness in a female character – and that cautiousness in a male character – is quite rare to see on the big screen.

"We talked about that quite a bit," explains Elba. "Let's not have Ben be the hero all the time, let's show Ben in weaker moments and let's show Alex in triumphant, typically masculine moments. But let's be truthful to honest gender dynamics. Especially in this day and age.

"Look - I've been playing characters that are masculine and machismo, and I've played a lot of those characters, and this is one where that's turned on its head."

This article was originally published in October 2017