It's a cold, wintery day when I meet Mark and he's wearing a huge, blue puffa coat, with a furry hood.
He approaches where I'm sitting in the cafe in a stealthy manner, head down, eyes scanning the room, and takes a seat opposite.
I've deliberately picked a table that is close to the wall because I know he will want to sit with his back to it.
"Yo, Sar" he says, smiling, as he sits down.
Mark is a gang 'older' meaning he has a level of seniority in a London gang.
He's 28 and has been 'on the streets' since he was fifteen.
But in Mark's terminology 'on the streets' doesn't mean homeless, it means that he is part of the criminal underworld that make money from the sale of crack, heroin, weed and any other 'hustle' he can spot.
Meaning violence - or a threat of it - is a part of his daily life. And it's this he's here to discuss.
I start off by asking him if he thinks life 'on road' is any different now than in 2008 when he was a fifteen year old 'new recruit'.
"It's 100% more violent" is his emphatic response.
"As a kid now, you're jumping in the game, entry level, you need a knife. Kids are carrying weapons. Every single person on the streets right now - it's compulsory to walk around with a knife."
And, he tells me, it's not just any knife.
"There's gotta be a connection between people dying and the weapons being used. People are using outrageous weapons to stab people. It's like Game Of Thrones. There's knives and they're that sharp… you wouldn't have to apply any pressure and you could cut a carrot - and everyone's got them."
But he dismisses the boys that carry these types of knives as "low-ranking criminals" or "soldiers".
"Serious people are not running around the street with zombie knives. This is kids with local beef, local beef. I walk with a flicky [flick knife]. Let's be real - man needs a flicky."
He says later, however, that he doesn't really want to carry a knife.
I've known Mark for 10 years now and we have a relationship built upon trust.
I learn about gang life from him and he learns about the TV news industry from me. I know there's no point in questioning him about the morality of carrying a knife, or pleading with him to stop.
I've done it a thousand times and he always gives me the same answer: "A knife is your security."
He doesn't really like to discuss it with me because he knows I disapprove, but we both know my disapproval and my questioning of his behaviour is not going to change a thing.
He lost a friend to knife crime for the first time at the age of 15, and when I ask him "how many friends have you lost since then?" he pauses and starts to count on his fingers.
"Close friends? About four. Acquaintances? Double figures, I couldn't even count how many people that I personally know that have been stabbed and killed.
"People I've played football with. People I've gone youth club with. We're talking 13, 14 people. At least one person a year."
He appears almost fatalistic about it. Not uncaring, but as if it's just a natural part of life. He describes attending his friend's funeral and thinking "wow, you can really be gone" and admits it made him more careful.
"It made me realise and be a bit more on point. I'm not going to go into an altercation without thinking that this person could have a weapon on him."
He accepts that losing a friend at such a young age has a psychological impact, and says: "It makes you more cold. When somebody close to you passes away, you almost feel like, well what else can be taken from me? You feel like you've got nothing to lose. And when someone has nothing to lose they become dangerous. What else is gonna frighten me? I've lost my friend."
And as a result of this kind of traumatised thinking, another young man is likely to bleed to death on a street.
I've seen the videos Mark has on his phone. Footage of boys who have just been stabbed. They are writhing on cold pavements, calling for their mothers, with blood spurting out of them and terror on their faces.
Children and young teenagers who are being filmed as they die and then the footage is sent around on Snapchat. But their deaths, according to Mark, instead of being a deterrent, might only encourage more young men to pick up knives.
"That changes the game completely," he says.
"One killing can make 30, 40 people in that area start to carry knives, because that could have been them."
Not only is social media being used to record the killings in 2021, Mark thinks that it's partly responsible for an increase in knife crime as well.
"People are getting killed because they are filming themselves walking down the road and their location is coming up. Someone sees it and says 'my man's on his own' which means man can get to him."
But it's not just the ability to find someone quickly which is increasing the killings, Mark says, it's also the fact that people feel the need to respond to being humiliated on platforms such as Snapchat and TikTok.
"On the streets I can't tell you how many people have been robbed. Beaten up. Stabbed. This is what happens. The difference between now and then, back then, you had the option to leave it alone. You had the option to say, 'you know what, I got beaten up, but f*** it'."
He says when he was 15 "violence would be quickly forgotten…but now the whole world will know about it, because they recorded you getting beaten up, 'we're not gonna let you forget about this, so every day you wake up we'll remind you that you got beaten up'. We (used to have) fights and lose. Nothing happened".
He says that today everyone is watching.
"You're a victim to the whole world. You're not a victim within your community. You're not a victim between you and the perpetrator, you're a victim that actually everybody in the world, all up and down the country, can see".
Even people like 'Ben from Shropshire' who he says, will be watching YouTube videos of gang "beef" in London and posting comments saying "yeah it's because he slept with this person's girl".
He points out that Ben from Shropshire "hasn't got a f****** clue what's going on, but if you read that, it's embarrassing."
"This causes a lot of violence on the streets," he continues.
"Human beings don't like embarrassment. Once they feel excluded because of embarrassment they will pretty do much anything to be let back in. And when you're living a certain type of life, or when you're portraying a certain type of life, the way back in might be more violence".
He also believes that the COVID lockdown has inadvertently ramped up the violence in 2021.
"There's a lot of people that have problems but because of COVD they didn't run into each other," he says.
"A lot of stuff got locked off, school, college, football, parties. What happened in COVID is a lot of these guys went online and might be talking s*** at each other. We're arguing every day. But when we meet it's gonna come to a head. But they weren't out, they were locked down."
He says some of these arguments were brewing in prisons too, and explains: "Most of these things start and continue in prison. Stuff can be settled in prison (but) a lot of things haven't been settled. The people that were beefing in 2019 are now settling it in 2021."
Mark has his own "war scars" from knife attacks.
"It shows you been through the war. You've been in the trenches."
He says he doesn't seek violence out and will avoid places which might be dangerous.
When I ask him if he would seek revenge for the death of a friend, he says: "I wouldn't go out and look for someone who did that to my friend to try and stab them. But I would be prepared to know that if I met them that would be the level it could get to. So I'd go prepared…if this is the situation, it's the situation."
A lot of the violence is disorganised, he says, with "kids running around with zombie knives".
"A mistake you make as a teenager could cost you your life in certain areas."
He tells me about a "younger" he knows who went out armed with a machete looking for the boys who stole his scooter.
"Would he have stabbed him if he found him?" I ask.
"100%" Mark replies.
But where are all the knives coming from?
"They're getting them on the internet. And selling them on Snapchat. You make good money off it."
He tells me that to get around a request for ID from websites that might make a knife traceable to the person using it, the gang members ask girls to purchase them online using their details.
"I can get a girl right now and get her to buy something. They might ask her for ID but she'll do it: and it doesn't come back to me... this is normal."
When I ask if these boys are deliberately stabbing to kill he says, "It's not good enough just to be prepared to stab someone, we're at a level where today people will laugh at you if you stab someone in the bum. You'd have to have an explanation for that.
"Because if you're telling me that this guy, who killed our friend, and you just stabbed him in the bum, you was better off not stabbing him. Because now I'm looking at you funny.
"You'd better stab him in the neck. That's what we rate on. Stab him in the chest or in the neck. People aren't gonna respect you if you're trying to stab them in the bum."
When I express horror at this advice, his answer is, "isn't that fair? I'm not saying that's the way to go about things. The reality is if someone hurts you, it's natural for you to want hurt them back."
Mark says he has been stabbed more than once and always recovered fully. One of the lucky ones. And he knows it.
"For all of those deaths you talk about there will be another hundred with life-changing injuries... the truth of the matter is, you're probably gonna be f***** as an individual after that.
"Your life's not gonna be the same. For a long time. You know these people they've got to have bags? When they go toilet? I know maybe three or four people who've had bags."
What he is talking about is colostomy bags that will have been fitted because a part of the anus or intestine will have been so damaged by a knife slashing through it that it just doesn't work any more.
"But you've gotta remember that being stabbed and surviving the stab can also be a positive. Someone's been stabbed a hundred times and they're still here to tell the story?"
He leaves the question hanging.
And what about those who don't just stab someone, but kill them.
"If you're prepared to kill someone you're gonna carry a lot of weight… most people would say, 'if someone hurt my kids I'd kill them.'
"What if no one hurts your kids? What if someone stole your drink? Stood on your foot? Because these are all forms of disrespect on the street."
He says the likelihood of boys talking to the police is almost zero because "they don't trust the police, it's a stigma to deal with the police" so instead "they'll probably deal with it themselves", which will mean more violence.
But he insists that it isn't just gang members who don't trust the police, but the majority of the black community.
"Remember when that white girl [Sarah Everard] got killed by the police officer? The country said 'oh my God, the police are corrupt.'
"We've been telling you the police are corrupt for 50 f****** years. Rest in peace, Sarah, don't get me wrong, rest in peace. But I'm not shocked that the police could do this.
"Not one f****** bit. How many police officers have killed people in a f****** police station? But people rather run with the narrative that it must be your fault. What did she [Everard] do wrong? But what did he do wrong?"
So why, I ask him, would anyone choose to enter this lifestyle, when, if you get to Mark's age in it, you will be unable to count the number of friends you've seen killed, because there's so many of them?
He tells me it's not always a simple choice about joining a gang. Some boys are affiliated without even choosing to be.
"What makes you gang-related in London, in certain areas, is you are in the science class with this guy. Of course you get on the 250 bus with him. It's the school bus. You're gang-related. He's in a gang. You're related to him. You've got an association. How can you grow up in an area that has a big gang influence without being gang-related?"
Other boys join in for a sense of "belonging".
"There's guys that go out and they don't feel loved by anyone. 100%. Especially in some of the communities we grow up in. Kids are having kids. Some people ain't got time to show empathy or love, because they're going through their own struggle as parents. Maybe their mum or dad is going through things."
And then there's the money that gang life can bring.
"There is financial reward, but a lot of these kids are earning more than their parents, let's be real," he says.
Mark's story is slightly different - he did feel loved and "accepted" in his home and his mother, who was a single parent (Mark didn't know his dad) worked as a nurse and so they had a relatively stable income.
"I always came from a family of love and knew what was right and wrong," he says.
But then his mother died when he was 15 and, he says, it had "the hugest effect on my life".
"Because up until that point I had never done anything without the intention of impressing my mum. If I'm at school, the first thing I did when I came home and aced a test, [was say] 'mum I've aced a test'. Nothing else matters. If I win sports day, it's my mum I wanna tell. After my mum passed away it made me feel, 'well what's the point?' I had no purpose.
"I felt like I had no purpose. And so I went looking for a purpose. If I'd had a teacher who had said, 'I know what you're going through, let me help you' maybe that would have become my purpose."
But nobody said to Mark "I know what you're going through, let me help you" and, after his grandmother died, he was left homeless by the age of 19.
He slept on night buses or on the floors and sofas of his friends, hustling for money by selling drugs.
Often I would try to assist him, by referring him to housing charities that looked as if they could help, but they would ask me: "Is he an ex-offender?"
He wasn't, in the sense that he hadn't gone to prison then, but when I would tell them "no, not yet" their reply would be "we're sorry we can't help him".
The council told him there was no duty to house him as he wasn't deemed "vulnerable", and offered him a hostel which had rival gang members in it.
They gave him housing benefit, which was capped, so he couldn't afford a room in London and every landlord he tried to get a room with anywhere would tell him "no DSS" - a reference to the now defunct Department for Social Security, and the term widely used to describe tenants who receive housing benefits to pay their rent.
It was a terrible thing to see. An intelligent young man who had recently lost his mother, his grandmother and his home, struggling to find real help, and getting sucked deeper into the gang.
Watching it happen taught me how little support and help there is available for people like Mark, and I ask him if he felt anyone had ever given him any real help since his mother died.
"My boys did, my boys did."