When Shane Milligan picks up the phone, the plasterer and part-time magician from Kent launches straight into an impression of a character he feels he embodies so fully that he sometimes loses sight of himself. “By order of the Peaky Blinders, this place is under new management!” he bellows in guttural Brummie from his home in Gravesend.

The line comes early on in Peaky Blinders, the Birmingham-set gangster drama that is about to come to a presumably bloody conclusion in its sixth series on BBC One and Netflix. In the episode, Arthur Shelby (played by Paul Anderson), the tortured brother of crime boss Tommy (Cillian Murphy), has just violently taken over a London jazz club owned by Italian capo Darby Sabini.

The scene, set in 1921 and written by the show’s creator Steven Knight, is classic Peaky. Arthur wears his sharpest tweed three-piece suit and tailored coat, his violent rage only slightly dislodging his tie from its penny collar. His trademark Peaky haircut – shaved back and sides, mop on top – is just so. There are screams and slow-motion sequences as the gang terrorise rich people in dinner jackets.

“Most days I’m dressed as Arthur,” Milligan says, returning to his Kent accent. He started as a fan of the show – and of Arthur – but was soon throwing out most of his modern clothes and picking up 1920s suits in vintage shops. He has the haircut and a dozen baker boy caps, albeit without the razor blades that, the myth goes (it’s not true), a real Birmingham gang of the same name used to weaponise their headgear. He has even turned up to work on building sites in his outfits, while also doing turns as a lookalike. “Even my nieces call me Uncle Arthur, it’s crazy,” he says. “But when I’ve got the gear on, I get that swagger, that walk. It gives me purpose.”

Since it landed on BBC Two in 2013, Peaky Blinders has become a huge popular hit while somehow retaining cult appeal. The fifth series premiered in 2019, in its first prime-time BBC One slot, reaching a total audience of 6.2 million. Netflix picked up the show in 2014, turning it into a global success. But what is striking is the extent to which it has penetrated and shaped the culture way beyond the West Midlands.

“I wish I could have a dime for every Peaky haircut I see here in Soho,” says Caryn Mandabach from her office in London. The American TV producer moved to the UK 15 years ago after producing US comedies including Roseanne and The Cosby Show, and her eponymous UK production company owns and produces Peaky Blinders.

There are no royalties in haircuts but Mandabach now commands a branding juggernaut. Peaky has spawned official festivals, video games, beers, escape room experiences, grooming products and Monopoly boards, as well as less official club nights, merchandise and vintage clothing lines. In 2018, the show was credited in the UK with boosting the popularity of the baby names Arthur and Ada (Ada Thorne is Tommy and Arthur’s sister).

The biggest fans don’t just watch Peaky Blinders, but lap up its stylised aesthetic and gangster mythology. “We had a group of 50 up from Birmingham just last night, all dressed up,” says Scott Blowers, a landscape gardener and Tommy Shelby lookalike. He gets paid every Saturday to drink in character and pose for selfies at Peaky Blinders, an unofficial themed bar in Manchester where £9 cocktails include “Arthur’s Punch”.

So while series six will be the last, the franchise will live on. A dance-theatre production, written by Knight and choreographed by the Rambert dance company, is due to open at the Birmingham Hippodrome later this year before a nationwide tour. A feature film is in the works. Knight has said it may spawn further TV shows.

Knight, a blacksmith’s son who grew up in Birmingham, has himself co-opted Peaky mania. In an unlikely sideline for an Oscar- and Bafta-nominated screenwriter who says he has no dress sense, he launched his own clothing line in 2016. Garrison Tailors (it’s named after the Shelbys’ pub) sells three-piece suits for £755 and caps for £69. “It’s astonishing that it’s had this effect,” he says of the show. “At no point did I ever think it would be like this.”

Mandabach remembers being disappointed by early audience figures. She and her production office had planned to pick a restaurant for a celebratory dinner with prices to match the launch ratings. “I forget where we went but it was pathetic,” she says. Vindication came quickly when a friend told Mandabach that her husband had tuned in with their 18-year-old son. “She said it was the first time they had talked about something together,” the producer recalls. “There was a depth to the way people liked it. They talked about it, it mattered … there was an affinity.”

Milligan was immediately sucked in. In the first series, set in 1919, a working-class family with Irish Traveller and Romany Gypsy heritage, amazing cheekbones and battlefield trauma from the first world war, fight and scheme (and invariably murder) their way out of poverty in the Small Heath slums of Birmingham. Eventually, they build a criminal empire and Tommy becomes an MP.

“The Shelbys are a family that do bad things but they’re trying to survive,” says Milligan, a youthful 61. He is from an Irish Traveller family and was bullied at school – until he started to fight back. He compares the Shelbys’ paradoxical working-class appeal as violent criminals in suits to that of the Krays. He is old enough to feel nostalgic about what he sees as a lost British era, but at Peaky events he’s struck by how many younger fans feel the same way.

“A lot of youngsters are drawn in by the gangster glamour,” says Carl Chinn, a professor of community history at the University of Birmingham, who grew up in the city in a family of backstreet bookmakers. His great-grandfather was a real-life Peaky Blinder. He now gives Peaky tours and talks in schools. Peaky Blinders draws on mafia tropes in which gangsters are “kind to children, respectful to the elderly, and look after women and their community”, adds Chinn, also the author of Peaky Blinders: The Real Story. “Poorer men owned nothing except their street. And masculinity becomes important in that; you show yourself to be harder than other people, that your street is tougher than the next street.”

Celebrity Peaky fans include Brad Pitt, Idris Elba, Tom Cruise and David Bowie, who once asked Knight to include his music in the show. David Beckham launched a Peaky-inspired line at Kent & Curwen, the old menswear brand he co-owned, at London fashion week men’s in 2019. “It just has this resonance all over the world,” Knight says. There are fan sites and Facebook groups originating in Brazil, Indonesia and South Korea. “But the moment I knew it was different was when Snoop Dogg asked to meet me and we spent three hours talking about Peaky Blinders and how it reminded him of South Central LA.”

Peaky’s biggest impact has been in Birmingham itself, where civic pride is fierce but rarely projected. “I think as technology and the economy moves on, a lot of people like to think about the origins of this place,” says Andy Street, another Birmingham boy and now mayor of the West Midlands. “There is a real affection that the show has tapped into.”

Before the pandemic, Birmingham was in the grip of a tourism boom that Street put partly down to Peaky mania. The city is on Hollywood’s map; Cruise was there last year to film his latest impossible mission. Knight is poised to announce plans for a new film studio in Digbeth, a thriving former industrial area close to Small Heath. “I don’t think any of this could’ve happened without Peaky Blinders,” Street says.

In 2019, the mayor himself wore a baker boy cap and joined 20,000 other fans in Digbeth for the first official Peaky Blinders festival. It included mock bare-knuckle fights, free haircuts and a fashion show for Garrison Tailors. Primal Scream and Liam Gallagher played – a nod to Peaky’s era-bending soundtrack. A sea of flapper dresses and furs showed that Peaky’s appeal is far from solely male. Women in their 20s dressed as Polly “Aunt Pol” Shelby (the late Helen McCrory), mob matriarch and head of a cast of strong female characters. “The whole district came to life,” Street recalls.

The Peaky look – increasingly available off the shelf (Birmingham’s branch of Primark did an official Peaky line in 2019) – clearly has a broad contemporary appeal. Tommy Shelby in particular has become, with a lot of help from Cillian Murphy’s face, an influencer a century before his time. There are also overlaps with other trends; Milligan is into steampunk, the retrofuturist steam-age aesthetic. The show’s interwar setting, which comes decades after the real Peaky Blinders’ reign, lets it explore not only the effects of shellshock, but the glister of the jazz age (think Gatsby goes to Digbeth).

“It’s not just about the look,” says Tony Williams, who in 2017 turned his successful party band (he played at Elon Musk’s second wedding, among other gigs) into Cheaky Blinders, a tribute act. “I’ve noticed that a lot of fans are people looking to be accepted. Dressing up makes them feel part of something, like they belong. It’s like being a football fan.”

The elephant in the blood-spattered room is violence. Peaky Blinders is brutal in the grand, blood-letting tradition of on-screen gangsterism. When Arthur announces that the jazz club is under new management, he does so while holding the limp body of its outgoing manager, whose face we have just watched him destroy with a broken wine bottle.

The show has periodically faced criticism for wobbling on the line between glorification and consequence. In an academic paper in 2019, George Larke-Walsh, of the University of Sunderland’s Faculty of Arts & Creative Industries, said Peaky promoted the “unashamed glorification of criminality”, using the excuse of postwar trauma and the romance of an underclass rebellion as a cover for gore.

The paper caused a stir, which surprised Larke-Walsh. When I call her, she says she is a fan not a critic. “I think the inclusion of the motivation of the war was brilliantly done,” she says. If anything, she adds, the balance the show does strike is suitably British; the Shelbys, she wrote, “play out the continual and contradictory conflict that occurs within this presentation of British national identity as simultaneously progressive and regressive”.

Chinn, the historian, is quick to try to educate the Peaky fans he meets. “Gangsters are always portrayed as flawed characters with admirable qualities – antiheroes who look after their own,” he says. “The real Peaky Blinders turned over their own community, preyed upon the poor and ruled the back streets with a reign of terror. These were not handsome, charismatic men; they were vicious, vile men.”

Chinn, who also celebrates the show’s impact on Birmingham, argues that any admiration should go to the women of the era, whom he credits for his own success. He says his Blinder great-grandfather was a domestic abuser. “The real heroes are the mums, the grandmothers, the big sisters, who daily strove for respectability and for a better world for their children.”

Murphy has admitted that Peaky is “working within the limitations of the gangster genre and things are heightened”. But Knight insists he is more interested in the scars – particularly the emotional ones – than the violence itself. “The biggest example is the violence of the first world war, the consequence of which carries on through six series,” he says. “It’s ugly, so we try to depict it as ugly.”

Knight has been amazed – at the festival and just while walking past the haircuts and caps during any stroll through Birmingham – to observe the impact of the world he has now nurtured for a decade. “But the great thing is, and I think this is an element of Englishness, is that everyone’s aware of their own absurdity, including me,” he says. “They’re not detached from reality.”

Milligan, who met Knight at the Birmingham festival, sits at the keenest end of Peaky fandom. Yet for all the sense of pride and belonging the mythology has brought him, he says it’s mostly just a bit of fun. He’s often heckled while walking around town in his Shelby get-up. “There’ll be lads walking down and they’ll say: ‘Oi! Are you really Arthur Shelby?’” Milligan prepares to switch back to Arthur’s Brummie drawl. “I’ll turn to them and I’ll say: ‘Whadda you think!’ And we’ll all have a laugh.”

Peaky Blinders returns on 27 February on BBC One.