York Hall, in London’s Bethnal Green, is one of Britain’s oldest boxing venues. Opened in the 1920s, it still hosts professional bouts in front of audiences of 1,200 people.

But in its near-century, the venue has never seen anything like the event that took place on Wednesday, when more than 1,000 teenagers queued to watch two of YouTube’s biggest stars – and rivals – trade insults ahead of their highly publicised boxing match next month.

KSI, a Fifa gamer turned internet personality, and Logan Paul, who found fame posting skits on Vine and is best known for mocking the dead body of a suicide victim in one of his videos, are big names on YouTube, with almost 20 million subscribers each. They’ve been sparring verbally for months, and after KSI defeated fellow YouTube star Joe Weller in a boxing match in February, fans began piling on the pressure for KSI and Logan to have their turn in the ring.

The whole thing is very silly, very theatrical and almost completely incomprehensible if you are older than 20. It is also huge. The fight will take place in the 21,000-capacity Manchester Arena in August, with tickets costing between £30 and £150, and it will be streamed on YouTube’s pay-per-view platform for £6, though the company has distanced itself from the event and is not commenting on the fight.

KSI, from London, will be defending his self-proclaimed title of YouTube boxing champion (claimed earlier this year following a third-round knockout of Weller) against his American foe Paul, with various members of the pair’s “squads” – including their brothers, Deji Olatunji and Jake Paul – also agreeing to fight each other.

Outside York Hall, an hour before the press conference is due to start, the queue is round the corner and down the street, with those at the back being assured they have no chance of getting in but continuing to queue. They are here for the chance to see their icons, and in this multicultural London crowd, that overwhelmingly means KSI and his squad, the Sidemen.

In fact, when one of Logan’s team – the Logang – drives past the entrance in a flash car, a spontaneous chant of “fuck Jake Paul” begins almost immediately, not dying down until the car is well down the street and into the side entrance.

Amy, 19, who came down from Newcastle for the event, and started queuing at 7.30am, described Jake as “arrogant and childish”.

“I’m not sure if it’s just a character he’s playing or if he’s really like that but I just don’t like his personality,” she said. Her friend Yara agreed. “They’ve been really controversial despite not having been on YouTube for that long,” she said. Still, the younger Paul apparently revels in it, later egging the crowd on and joining in the chant when it restarts as he takes the stage.

It is not hard to see why they rub people up the wrong way: the pair got their start with six-second pranks on Vine, before moving on to bigger and better things, both virtually, trading Vine for YouTube, and physically, moving from Westlake in Ohio to LA.

Since then, they have been constantly in the press for their antics, from manufactured drama for their YouTube channels to real drama with their neighbours.

Last July, Jake’s $17,000-a-month (£13,000) rented home played host to a stunt involving a burning pile of mattresses that was the final straw for many of those living near him.

Logan has perhaps been less deliberately obnoxious, but the same thoughtless attitude has brought him as much trouble. In January, YouTube disowned him and demonetised his channel for a stunt in a suicide hotspot in Japan that saw him laughing and joking around a body.

There is also a geographic element. KSI and Deji were playing to a hometown crowd, and they knew it. “Welcome to London, motherfucker,” Deji shouted as he came onstage to square off against Jake.

Although billed as a press conference, the real audience were at home watching, which meant the whole affair was more of a pastiche of a boxing press conference, as filtered through news broadcasts, films and highlights of previous matches.

That did not stop the crowd from getting into the spirit of the event. Standing in the front row, Joe, a high-school pupil, said: “KSI’s a thrasher, right, but Deji’s too small to be fighting Jake Paul. Props to Deji for going for it, though.

His friend Jordie disagreed. “Everyone said that Joe Weller was going to beat the shit out of KSI, and look what happened, so Deji … tank. Tank gang,” he said, referring to a music video with the same name put out by Deji in December.

The rivalry, though profitable, also seems sincere. When KSI arrived on stage he picked up Deji’s lead, hurling abuse – a mix of theatrical and apparently genuine insults – at Logan, but the older Paul brother is either too outgunned by the crowd, or too cowed, to fight back.

He sits, mostly in silence, as the insults become personal – KSI turned at one point to the father of the Paul clan, himself a minor internet celebrity, and asked “how do you make not one, but two, dumb-ass children? What the fuck is wrong with your sperm?” – and the audience gets meaner. KSI brings up Logan’s new girlfriend, the actor Chloe Bennet, and the crowd spontaneously starts chanting “she’s a slut”. Eventually, Logan drops the mic and walks out, seemingly on the edge of tears, cutting the event short.

The crowd clears out, and Logan flees in a bright yellow Rolls-Royce. But it is not quite the end: hoping to see more of KSI, half the audience ascends the stairwell of a neighbouring housing estate, while the rest cram up against the gates of the car park. The YouTubers cannot get out, the teens cannot get in, and there is gridlock – until someone starts chucking construction debris from the roof, the stars are shepherded back in, and the police are called.

Despite that, Yara is happy with how it went. “In terms of the actual conference, I’m biased in saying this, but as a fan of JJ it was great. Most if not all of the audience were rooting in his favour, and both JJ and Deji did get to say what they wanted to say to Logan and Jake,” she said.