The Irish actor is back on the small screen as the glamorous and ruthless gangster in the Birmingham-set drama. He tells Susan Griffin why, bar that haircut, it's a gift of a role

The first series of Peaky Blinders was described as the 'anti-Downton', and no wonder, given its early 20th century gritty gangland setting, stylistic tone and slow-motion set pieces, which set it apart from more staid period dramas.

And then there was the stomping soundtrack, which included music by Nick Cave and Jack White.

"I have to admit, initially I was like, 'You're putting contemporary music with a period drama?!' But it worked, because a lot of the artists had an outlaw quality to them, and that seemed to suit the essence of the show," says Cillian Murphy, who plays Tommy Shelby, the ambitious head of Birmingham's criminal gang, Peaky Blinders.

The Irish actor, who lives with his two sons and artist wife in London, believes the success of the show developed in the very best of ways – through word-of-mouth.

"It was only on for six weeks, but people were telling people to watch it. That's what you want, rather than things being shoved down your throat."

Wearing Tommy's sharp suit, Murphy's androgynous features and huge blue eyes make a mesmerising combination, not least when topped off with the Peaky Blinders' distinctive haircut – shaved sides and longer on top.

"I was alarmed by the haircut, I have to admit, but I'm contractually obliged to have it," he confides, grinning.

In series two, time's rattled forward to the early Twenties, and an edgier "cocaine feel" has replaced the dreamy, opium-infused ambiance of the first run.

"Cocaine was widely available and popular among the upper classes, and obviously it was being distributed by the gangs, so I think that's informed the tone of the series," agrees Murphy. "Also, Tommy's moved on from that crutch of opium, although I think he's still boozing it up and has his issues."

Creator Steven Knight, Murphy and the rest of the team wanted the follow-up to be bolder, as with any sequel – so this time, the Peaky Blinders venture out of Birmingham and head to London.

The new series also sees the arrival of new faces, including Hollywood star Tom Hardy and (his rumoured new wife) Charlotte Riley.

"It feels like you've done something right when you get great actors like that onboard. I knew both from before; it felt like working with people you know and trust, so it was a lovely atmosphere," Murphy adds.

He'd be loath to give anything away about Hardy's "creation", but "suffice to say it'll be memorable", he teases.

The chance to reunite with the original cast, including Helen McCrory who plays Aunt Polly, was also a bonus for Murphy.

"Helen puts in an astonishing performance this season. We see the conflict in her, being this woman and a gangster and trying to marry those two," he says, before joking that their characters' relationship is even more complicated this time round.

"She's obviously the matriarch but she's not his mother, she's his auntie. And there's not much of an age gap between them, and that causes tensions."

But she also understands him more than anyone. "So although she's a thorn in his side, she's the one person he trusts."

All credit to Knight for creating such strong female roles, and for achieving sympathy for characters who, on paper, we should detest. "None of these characters are perfect or infallible. Even though they operate in extreme environments and have moral codes we could never subscribe to, at the same time, we see their weaknesses, foibles and desires," says Murphy.

"What I like about Tommy is that, even though he's a power-hungry gangster, he's really vulnerable and broken inside. He's a man who left all beliefs behind in muddy France, any respect for authority, any faith, and came out a man who fundamentally isn't afraid to die. And that's a great thing to play, because it informs everything. It's not nihilistic, it's fearless."

"I've always been interested in playing characters that are, if not outsiders, at least ordinary people in extraordinary circumstances," he says. "That's always been more appealing to me, and there's a happy coincidence now, as that seems to be a lot of the characters in television."

Cameos in the Batman franchise aside, Peaky Blinders marks the first time he's returned to a character, and he hopes a third series will be commissioned. "Steve has a plan up until the Second World War, and I love Tommy. These are the sorts of characters you search for; great, meaty, complex parts."

That said, a short break is welcome: "It'd be nice to know you're coming back, but it's also quite nice to have a break," Murphy admits. "Tommy's quite intense!"