Why the rich and famous love Peaky Blinders

This series, we are promised “international consequences” and Paddy Considine as Father Hughes – “probably the most evil person we’ve had in the series” – in what has always been big, bold, ambitious television with a sleazy modern beat and a deep sense of its own iconography.

Episode one began, back in 2013, with Tommy riding a black horse bareback down a terraced slum to the gothic strains of Nick Cave’s Red Right Hand: “He’s a god, he’s a man, he’s a ghost, he’s a guru, they’re whispering his name through this disappearing land.”

As I watch out of the library window, Tommy rides again, in a poetic echo typical of the show’s self-belief. Except this time, the horse is saddled and clip-clops down the long, ornate gravel drive of the stately property Tommy and his surprise new wife now call home, while Ada and Michael wait in line to see him, just as Don Corleone’s family had to in The Godfather.

“You didn’t come on a very exciting day for Tommy!” Murphy chuckles when we repair to his trailer for a warming cup of Rooibos tea (“I controversially have milk in it.”) Pinned to a wall of Murphy’s trailer are five sheets of A4 paper on which a director, Tim Mielants, has meticulously drawn an arrow-streaked map of “Tommy’s journey” over series three. “Don’t look too closely,” he warns of the spoiler minefield. Within a complex narrative necessarily shot in a random order, it tells him YOU ARE HERE. “You really have to have your thinking cap on. You’re so immersed in it, you dream it.”

So why do we want to be in Tommy’s gang? He murders, lies, extorts and destroys. At the end of series two he used lovestruck reformed prostitute Lizzy to honeytrap a field marshall at the Epsom Derby, leading to her sexual assault. Surely it can’t be as simple as everybody loves a bad boy?

“I’m aware that his actions and his principles are completely at odds with mine and with those of society’s,” Murphy ruminates, choosing his words carefully. “But there is something about him that is compelling. It’s the flawed and contradictory nature of his character. And you get to spend so much time with the protagonists of television, as opposed to two hours in a film, you can go deep and see the reasons why he makes certain decisions. For me, that’s drama. I don’t think a good man’s life is particularly interesting to read about or to watch.”

It’s worth remembering that brothers Tommy, Arthur and John came back from the trenches, where, as Knight says, “killing people is nothing”. Chatting to Paul Anderson, who elects not to grow his own moustache for the part so that he can leave the unpredictable, self-medicating Arthur in the makeup chair, he reminds me, “Post-traumatic stress disorder didn’t even have a name after the war.” Murphy adds, “Tommy doesn’t care for authority, he’s godless, and he has this capacity for violence, but those attributes came through the Great War.”

I ask Helen McCrory, who states that this series is Knight’s most “psychologically complex” and relishes its Catholic themes of guilt and damnation, what she thinks draws us to the Peaky Blinders?

“Their need to succeed. Their passion and loyalty to each other, and the knowledge of the desperate world they come from – it allows you to empathise with them. It was a grim and horrible life and it’s the Herculean strength it takes these people to get through it that makes them heroes.”

For Knight, it’s even more fundamental: “They’re free. They’re not going to work. They’re not getting on the train. No one tells them what to do. They’re ruthless but I think there’s a line, and in series three, we get very close to that line and look over the edge into the abyss.”

Peaky Blinders starts on Thursday at 9pm on BBC2