SToke Newington on the eve of derby weekend is not for the faint-hearted. Situated in the midst of a bitter turf war between historic rivals Arsenal and Tottenham, even on a sunny Friday lunchtime, its leafy parks and terrace-lined streets brim with menace. Take a wrong turn or get looked at the wrong way and no one can really predict what will happen next. A King Charles Spaniel howls wildly on the way to Clissold Park. The blood on the pavement outside the bakery turns out, on closer inspection, to be jam from a doughnut.

Such is the omertà surrounding this 111-year-old feud, which resumes at Tottenham Hotspur Stadium on Sunday afternoon, that local business owners are feigning impartiality or even ignorance about the upcoming match, presumably out of fear of reprisals from opposing fans. “Are Spurs playing Arsenal this weekend?” asks a woman arranging the display at a local flower shop who gives her name only as Laura. “I’m not a big football fan.”

No one at the local estate agent says they’re interested either, although a guy further back – whose identity I’ve protected for his own safety – thinks Arsenal could be in trouble without Martin Ødegaard.

Undeterred, the observer has set out to find out what makes this derby one of the most hotly contested rematches in all of professional sport. For the millions of viewers watching on TV around the world, it’s simply 90 minutes of product, with all the hype and gossip that goes with it. But for those involved, it’s much more than that. It’s a way of life.

That’s why this newspaper has decided to step out of its comfort zone and into the often mythological but largely unexplored wilderness known as ‘North London’. Who are these people? What drives and fulfils them? And how has football restored some pride to a region better known for centrist politics and open water swimming?

Three miles away, at the Coach & Horses pub on Tottenham High Road, the chalkboard above the bar is adorned with memorabilia, from signed shirts to flags. This is Spurs territory. A sign hanging around the whiskey dispenser reads “Home fans only.” An Arsenal fan entering this pub would literally be risking their life. It’s only midday, but a few diehard regulars have already taken their usual seats at the back of the room.

To break the ice, I ask if they are Tottenham fans. “Sunderland,” one replies. “Shamrock Rovers,” says the guy next to him with a Dublin accent, a wrinkled and friendly old man who later says his occupation is “male model.”

“I’m the only Spurs here,” calls the landlady, a pleasant middle-aged woman called Tina. As you can imagine, running a Spurs pub on derby day is not a job for the faint-hearted. The Coach & Horses will be packed and security will be hired to keep order and enforce the rule that no away fans are allowed in the pub.

But what about the rest of the time? What if an Arsenal fan – known pejoratively in these parts as a ‘Gooner’ – crossed the threshold? Would they simply be thrown out? Or would a more exemplary punishment be required? “Oh, that rule only applies on match days,” Tina explains. “We have Arsenal fans here all the time. There’s one over there. She’s my daughter.”

She points to the other end of the bar, where a young woman is on the phone. It turns out that Tina is a very rare specimen: a Tottenham sleeper cell. Her whole family are Arsenal fans. She even lives in Holloway, in the shadow of the Emirates Stadium. So how did she end up being baptized in Tottenham church? “Because I’m special,” she says.

As with so many intractable conflicts, no one really knows where the battle lines lie. Hornsey and Finsbury Park are clearly Arsenal, Stamford Hill and Seven Sisters are more Spurs. But even within these broad distinctions there is room for nuance. There are Spurs fans who live in Holloway and Arsenal fans who live in Walthamstow. Essex and Hertfordshire are contested areas. Rival tribes often live side by side, sharing the same workplaces and schools, even the same bed.

The potential for skirmishes, even full-blown violence, is endless. Like many of the world’s great derby cities – Glasgow, Rome, Buenos Aires, Belgrade – north London must feel like a powder keg, constantly on the verge of exploding.

“But that’s religion, isn’t it?” asks an Arsenal fan in the Little Wonder cafe just off Holloway Road. We made the short trip south to the Arsenal grounds in search of the opposite perspective on this eternal civil war. “It’s not like that. It’s just banter. Showing off. I mean, there are always a few idiots who cause trouble. But we don’t want to hate each other.” “I don’t know,” his friend replies. “Tottenham fans are just different, aren’t they? Somehow. I can’t really explain it. Maybe it’s moral fiber.”

Perhaps the deadliest conflict in the recent history of the Arsenal-Tottenham feud occurred almost a decade ago, when a supposedly joyous victory parade to celebrate Arsenal’s FA Cup triumph ended in ugly scenes. An Arsenal player named Jack Wilshere addressed the crowd outside the Emirates Stadium and began a familiar anti-Tottenham chant. “What do we think of Tottenham?” he asked. “Shit!” came the reply. “What do we think of sh*t?” he continued. “Tottenham!” “Thanks!” he replied.

In the ensuing uproar, the club’s television channel was forced to stop broadcasting the parade live. Internal disciplinary proceedings were initiated against Wilshere and he left the club less than a year later.

Mark Doidge is a sociologist at Loughborough University and an expert on football fan culture. “Football is a great way to understand how social groups form,” he says. “Who We are, it is partly about what we do together with others like us. But it is also about who we are notRivalry is therefore about the right to show off, symbolic superiority over others, to affirm who We Are.”

Why then do some rivalries incite fear and carnage, while others seem so contrived, almost forced, and based entirely on banter and irony? “This is partly down to cultures of masculinity and hooliganism,” says Dr Doidge. “Basically, the fans themselves bring emotion and intensity to the spectacle.”

“The more they care – the more their identity is tied to the club, what psychologists call a ‘fused identity’ – the more likely the rivalry will spill over into events off the pitch. Perhaps the north London context offers fans other ways to develop an identity outside of football? That is, they feel less hurt by defeat?”

On Sunday, police cars and horses will be out in full force again, expecting trouble. Broadcasters and social media accounts will remind us that this is a blood feud, a dynastic dispute almost as old as north London itself. Many of the fans who flock to Tottenham from Islington and Stoke Newington, from Hackney and Heathrow Airport, from the suburbs and the Home Counties, will have paid hundreds or even thousands to secure their place: a measure, perhaps, of how deep the passion runs.

Then a whistle blows and the conflagration begins: two tribes that deeply despise each other, or at least feel they probably should.