The dark horse Idris Elba is back for the fourth season of crime thriller Luther

Idris Elba as detective chief inspector John Luther in the crime thriller Luther. Steffan Hill / BBC America via AP

Idris Elba has many reasons for why he keeps returning to the BBC's crime thriller Luther, the fourth season of which was broadcast in Britain and the United States last week.

"It's unfinished business, it's fertile ground," he says. "The character continues to challenge me." The 43-year-old British actor shot the latest series – if two new episodes can be considered a series – of the BBC's dark detective thriller before travelling to Dubai during the summer to film Star Trek Beyond. He says he can't talk about the sci-fi sequel, beyond confiding that "it was fun and different, especially after shooting Luther last spring".

Despite increasingly becoming a marquee name on the big screen, Elba says the troubled character of detective chief inspector John Luther continues to intrigue him.

The complex and brooding character also challenges his fans, who greeted his return warmly last week, although those in the UAE will have to wait – a broadcast date here is yet to be set.

In his latest outing, Luther once again finds himself consumed – possibly in more than a figurative sense this time – by a grisly murder case: a serial killer with a cannibalistic bent.

He also remains haunted by Alice Morgan, the tantalising sociopath from Season 1 who escaped arrest by Luther and became his twisted confidante – and occasional helper. Conspicuously missing after the events of season three, she remains very much on Luther’s mind and a key part of this latest tale.

Elba describes the dark, brooding, demons-beset Luther as “one of the closest characters in terms of who I am”. It’s a surprising admission, since he seems light-hearted during our interview, wearing stylish casual wear, a marked contrast to the glum expression and no-nonsense suit and long, dark jacket Luther normally wears.

“I don’t feel like I have to throw on too much of a character to play John Luther,” says Elba, attempting to explain himself. “We shoot in the area I grew up in [East London], and I really let the writer take me on the journey. It’s the most naturalistic I can be in a role.”

Even Luther’s distinctive walk – a slouching swagger, hands jammed in his pockets, pushing forward with staunch determination – is derived from Elba’s own gait: “I tore my left Achilles, which makes my left leg sort of limp – or swag.”

A strapping, towering presence, with leading-man looks, Elba nonetheless has been able to transform himself profoundly for his roles. He was the brutal ­leader of an African rebel army in the recent film Beasts of No ­Nation, portrayed Nelson Mandela in ­Mandela: Long Walk to Freedom, and was Stringer Bell, the strictly business Baltimore drug lord in the HBO series The Wire.

Asked if he gets weary of his extreme good looks being the focus of media and fans alike, he adopts an almost sheepish expression while giving all the credit to the camera.

“Because I’m an actor, I’ve got that ‘beauty light’ on me,” he says. “In real life, it’s not like that all the time. Some people go, ‘He’s nice, but he’s not my sort of thing’.”

Acknowledging that too much attention to his looks could paint him as just another pretty face, he allows that “it’s a ­compliment and it’s great, man. I could be described as ‘aggressive,’ or ‘strong’.”

After acting for more than 20 years, Elba says he has only recently come to understand what drives him as an actor.

“I’m a person who absorbs a lot, takes in a lot of information every day, and with that comes an urge to let it go,” he says. “As an actor, I get to expel all that stuff by throwing it into my characters. “Before I figured that out, I think I was motivated by the dream of being famous. But now I see that I do it because it’s therapy, as well.”

Luther’s next adventure could be on the big screen. Elba states he is longing to let Luther loose on a wider landscape than the streets London.

“The ultimate goal is to end up with him in a film,” he says.

“New York could be an amazing backdrop for John Luther.”