The rapper's track that sparked a wave of killings

When a video of an attack on one of the UK's biggest rap stars went viral, three young people were murdered in the London borough of Haringey over the next 10 weeks. Tensions have long existed between rival gangs in Wood Green and Tottenham, but they rapidly escalated two years ago as tit-for-tat attacks were filmed and posted on Snapchat and YouTube.

Ken (youth worker in North London): There's a dispute between Tottenham and Wood Green. This has been going on for a number of years. It's a postcode war - N17 versus N22.

I'm hesitant to call them "gangs" but the violence is specifically around their lifestyle, the music and the disrespect that they've shown to each other - all played out on social media.

Johnny (young man from Tottenham - not his real name): I don't believe a truce will ever be made between the two sides, cos it's always just tit for tat, d'ya know what I'm saying? They're at war cos they've lost friends, they've lost family members. It's just like the Bloods versus the Crips man!

Nelson (young man from Wood Green - also an alias): They call it a "beef war". Headie One is a rapper from Tottenham. They [attacked him] at a university [in Luton] and they filmed it. If you're from Wood Green it's, "Yeah, we've got one up." They're scoring points. Then there's a chain reaction. The other side is going to retaliate.

Ken: A short space of time after what happened at the university, we're looking at [posts of] another violent incident. A young man has been shot in the neck. This is all done to humiliate, it's done to intimidate. It's to say, "You touch one of us, we'll come back and touch you."

The shooting took place in Wood Green on Saturday 27 January - the day after the video of Headie One being attacked in Luton was put online. The man who was shot in the neck survived, as did a second shooting victim. A video taunting Wood Green was posted immediately.

And the day after that - Sunday 28 January - Headie One uploaded a track, Know Better, to YouTube. It was later released by Sony imprint Relentless Records.

Ken: That song is disturbing to me, because it's quite clear that what he's actually pushing out in the song is what apparently took place: a "loss" in Luton, a "win" in Wood Green. There's such a close connection between what's happening and how they put it into verse. That track now has nearly nine million views on YouTube.

Nelson: Headie One, he's come out of nowhere, he's made this song. Now it's all over Radio One but they're not understanding the lyrics in that song. A loss in Luton, a win in Wood Green. He's referring to that person that got shot in his neck.

What's being said are facts relating to real people, what he is saying is real. That person that got shot in his neck, his parents got to listen to that. Everyone from Wood Green knew exactly what he was referring to. Everyone was upset. Even if you wasn't exactly a gang member but maybe an affiliate or just someone from the area, you was upset.

I don't want to knock anyone's hustle or way of getting legit and bettering their life. Music is a way for a lot of people. But everyone was tense.

On Saturday 3 February, 22-year-old Kwabena "Kobi" Nelson was murdered in Tottenham.

Ama (cousin of Kwabena "Kobi" Nelson): I essentially found out on Snapchat. I started seeing posts - broken heart, broken heart, broken heart. And then people were DM-ing me "Sorry for your loss. Sorry for your loss. Sorry for your loss." And I'm like, "Sorry for what loss?" Then I got the call. I was like, "What do you mean Kobi's been stabbed?"

Kobi was my younger cousin. He was all about bringing communities together. He was a youth worker. He passed away on 3 February 2018.

I know this happened [because] of what's been going on in the community - the knife crime and stabbings. Why it's happened to Kobi is what I don't understand. Kobi wasn't involved in any gangs. But living in Tottenham does make you more susceptible to certain situations, and this is one of them.

Ken: I did know Kobi. He was doing a lot of work with young people who were caught up in that lifestyle, trying to get them to turn their life around. But Kobi became, by association, a high-value target and happened to be in the wrong place. It's unforgivable what was done to Kobi, he was a man of peace. He wasn't involved in violence but you don't have to be involved to get caught up.

Ama: When they told me Kobi was dead, I was just in shock. It was right by our childhood park, so where we had a lot of memories. To know that's also the place where he lost his life, it really cut deep. Every day is still a hard day. It's just that you get better at dealing with it.

Nelson: I honestly don't know but I can say wholeheartedly I kind of feel like if those posts and that song didn't go out, the tension, or the intention, wouldn't have been this situation for Kobi. There is a very strong chance that it might not have happened, because there wouldn't have really been no fuel added to the fire.

Listen to Oliver Newlan's File on 4 documentary, Taking the Rap, presented by Livvy Haydock, on BBC Sounds

Ama: Drill has never been my kind of music because I can't really relate. I can't stand listening to songs where people are just saying: "I'm gonna kill this person, I'm gonna kill this person."

When I learned about the Headie One thing I knew there could be retaliation. I don't want to solely say it's because of that song. I believe that it had a huge bearing on the fate of Kobi, but it's not the only factor. The young people in our community are traumatised.

On 8 March 2018, five weeks after the murder of Kobi Nelson in Tottenham, 19-year-old rapper Kelvin Odunuyi was shot dead outside the Vue cinema in Wood Green. Police believe the second murder was a direct response to the first.

Kai (Kelvin's brother): Kelvin was pretty cool - he was calm, peaceful. He was a nice little loving brother of mine. Unfortunately with all the gangs and everything that came in after we moved to Wood Green, it went sideways very quickly and he changed - he changed for the worse, in my personal opinion.

Ken: He put a post on social media outside where he was standing, you know, which also gave the location where he was at. And within 15 minutes of him posting that last post, then the guys ride up on him. They came up on a moped, you know, on to the actual paved area, and they actually did what they did.

Kai: A mate of mine texts me saying that something happened to my brother. I was like, "What do you mean something happened to my brother?" I realised my mum and nobody was in the house. I was like, "What happened?" Then I found out, when they come back, that my brother had passed away.

I couldn't think straight always, I was completely depressed around that time, like completely - especially because of all the people bad-mouthing him on social media. People were cussing him out on his deathbed, all of that, saying, "Come threaten the family. Come do us in." It's just not right.

On 2 April, 17-year-old Tanesha Melbourne-Blake was shot dead in Tottenham. Police believe her death was linked to the gang feud.

Hakeem (Tanesha's brother): I literally just got back from university. I just put my bags down and then I got a phone call from my brother saying that she got shot, but I didn't really believe it.

I went straight down to where she got shot. We ended up pushing past the police, jumping over the walls, and then we realised it was her. She was on the floor. Even just picturing it now, I still don't believe it.

Ken: A young lady with all her future ahead of her lost her life, only because she was standing in the wrong place at the wrong time. And she wasn't the intended target, I'm quite convinced of that.

Hakeem: She was spontaneous. She was just a bubble of life, really. She was always singing, always wanted to make something of herself.

Ken: I have been out there for almost 15 years, and that time resonates with me, because of the intensity and the regularity of the violence. It was senseless, it was savage, it was uncalled for, and I really don't want to see a period like that ever again in my lifetime.

I don't believe that social media was the only factor but I believe that social media ignited the actual explosion that was experienced around that time.

Drill artists that make money from producing lyrics that glorify someone losing their life - it inflames the situation. It gives out the wrong impression that this is what we do in the black community. This is not what we do. We're fed up seeing this type of violence in our community.

Hakeem: I'm basically trying to do a [TV drama] series which shows how a person's life can change - and how to break the cycle of violence. It's a matter of who's willing to break the cycle, cos people can't themselves - literally, they need a pioneer.

Ama: I always felt as if, at some point, I was going to give back to my community or work with my community. But when you lose a family member in this kind of way, it creates an urgency, you know, it's not something that can now wait. This is something that needs to be addressed.

I deliver mental health first aid training. I developed a capacity-building programme in schools, in church, in Haringey, to empower young people to have positive aspirations.

When I wake up in the morning and I see the young people on the streets, I see the young people getting on the bus going to school, that is my hope.

The BBC asked Headie One to comment, but he declined. Snapchat says it takes swift action when offenders are reported and that it works closely with the police. YouTube told the BBC it was working with the Met Police and the Home Office to tackle gang-related content.

Neron Quartey from Wood Green is serving a life sentence for the murder of Kobi Nelson - but the investigations into Kobi's death, and the deaths of Kelvin Odunuyi and Tanesha Melbourne-Blake remain active.

Interviews by Livvy Haydock, additional reporting by Alys Harte