By Gavin Lee
BBC Radio 5 live
Trouble flared up around the game between Millwall and West Ham
Fighting between Millwall and West Ham football fans was planned a fortnight before the match, the BBC understands.
A Millwall fan who said he organised some of the violence said fans phoned rival supporters arranging to meet.
Police say nine people have been charged after "large-scale trouble" at West Ham's Upton Park on Tuesday night.
One man remains in hospital in a stable condition after having been stabbed in the chest. Two other men were also taken to hospital with minor injuries.
Fighting broke out before and after the match and there were several violent incidents inside the ground.
CCTV footage of the night is being examined by police to identify people involved. It is expected to take months to complete.
One man, a member of a Millwall football gang, told the BBC the violence was being organised as soon as the two clubs had been drawn together.
"About a minute after it came out, that was it. My phone was red hot, my Facebook went into meltdown.
"It was everyone I know texting me, phoning me and I was phoning people. I went to work the next day without sleeping. It's one of those things you dream about. A night game at Upton Park."
The man, in his mid forties, asked for his identity not to be revealed in fear of reprisals from other gang members.
He was also involved in the violence between football fans in the 1980s and says the match between the two sides has a history to it.
"I suppose the violent side to it, there's been a lot of previous.
"In the 70s the Inter City Firm (a West Ham hooligan gang) were very organised and businesslike.
"And when Millwall played West Ham it was like, we can't let them get on over us. There was bitter rivalry. Very violent and there's been a lot of incidents back and forth over the years."
History of violence
He says he was in contact with fans involved in the violence during the 70s and 80s, who were organising fights to take place with rival football supporters on the day.
"A few members of the firm have a few numbers of the other firm. It's the top boys.
"They've got each other's number for one particular purpose. They haven't got each other's number to say do you fancy coming out for a beer. They have them for specific reasons, and that's that."
The Metropolitan Police says it is aware that some aspects of the trouble were pre-planned.
A source close to West Ham United also told the BBC an investigation is being carried out into claims that hundreds of Millwall fans got into the match without tickets.
Fans invaded the Upton Park pitch during the match
According to the Millwall fan involved with fighting on the night, one of the away gates was forced open.
"The main Millwall firm of about 450 got picked up half a mile from the ground and put in a police escort.
"They broke away from the escort. They were just outside the away end and there was a few more without tickets. And they just stormed the gate."
But the Metropolitan Police said it was "not aware of a large number of Milwall fans forcing their way through the gates or turnstiles before, during or after the match".
The fan also denied that his group had any involvement in the stabbing of a 43-year-old-Millwall fan, who was attending the match with his family. He claimed that a separate group of fans were influenced by events on the night.
"The pictures in the papers, the fans running onto the pitch, that's not hooliganism.
"The firm is not interested in family supporters, people wearing scarves or colours. They're after like minded people who are there for the same reason."
When asked if he felt ashamed about putting people's lives in danger and ruining the sport for football fans, he acknowledged that it was ruining games but says the West Ham and Millwall derby will always bring out a hooligan element.
"Looking at it from an unbiased perspective, it is quite sad people can't go to a specific game for fear of being stabbed.
"If we got West Ham again you're gonna have the same people going. People that shouldn't have gone. People without tickets. You'd have the same day."
The Metropolitan Police said evidence suggests the Millwall and West Ham violence was an isolated incident and does not signal a return to the hooliganism seen in the 1980s.