Believing that the youngsters died after a firebomb attack by racists, and infuriated by two months of apparent police indifference, 20,000 people joined an extraordinary, almost spontaneous march from south- east London to Hyde Park.
The "New Cross 13" preceded Cynthia Jarrett, Joy Gardner and Stephen Lawrence on the roll of black victims mourned by civil rights campaigners in the past two decades. But the case's status as an anti-racist cause celebre may be over. A forensic science report last week identifies the source of the fire as a foam-filled armchair in the ground-floor front room.
The report, based on an investigation using highly sophisticated computer technology, has ascertained the precise minute when the fire started and has finally scotched the belief that firebombers were responsible. It suggests that the blaze was begun, intentionally or otherwise, by someone present at what had been an all-night birthday celebration.
George Francis, the chairman of a committee set up by the parents of the victims, said last week that he and the other parents were now satisfied that racists were not involved. "It's true most people believe that the fire was caused by the National Front and the police are withholding this evidence, but I don't agree," he said. "There was no petrol bomb at all."
The significance of the fire in the black community cannot be overestimated. Trevor Phillips, the black broadcaster, has described it as "the terrible solidifying event of the Eighties" and, just before he became a Home Office minister, Paul Boateng said of the fire: "It was a devastating event for the black community and believed to be a racial attack."
The police investigation into the fire, which broke out at around 5.50am on 18 January 1981, was reopened 20 months ago after continued pressure from the families. An inquest in May 1981 recorded an open verdict.
Detective Chief Inspector Peter Newman, head of the new inquiry, said yesterday: "The forensic scientist has totally rejected a petrol bomb, explosive or timed device."
He said that officers were tracing and interviewing all 60 people who were at the party after 5.30am.
Despite the passage of 18 years, many of the partygoers have provided far more detailed accounts of the night's events than during their original interviews. This is partly because of improved police interviewing techniques and partly that the first police inquiry took place in an atmosphere of high racial tension and bitter antagonism between the police and some sections of the black community.
A New Cross Massacre Action Committee was set up, favouring the firebomb theory and accusing police of trying to pin responsibility on one of the partygoers. Several guests refused to co-operate with police. One man, traced to New York, denied he was at the party at all, despite accounts from others that he was.
Police have now determined that only 30 people were in the house by the time the fire started. DCI Newman said: "We are using the latest analytical computer packages to piece together the movements of everybody in that house to work out the windows of opportunity for starting the fire."
He said that a significant amount of evidence had been uncovered which was not available to the coroner at the inquest. "There's no evidence of any outsider sneaking into the house or throwing something into the house," he said. "The scientist says that in his opinion the fire was started by the application of a naked flame to a specific armchair."
Some members of the black community, however, remain unpersuaded even by the new evidence.
Andrew Morris, who stood as an independent black candidate in the last local elections and lost a cousin in the fire, told the New Nation black newspaper: "I don't believe DCI Newman." He said: "He knows that the fire was caused by racists probably throwing a Molotov cocktail through the window and he's just trying to cover it all up. I'm convinced it's a racial attack - there were similar incidents in the area before and the perpetrators were never found."
The view is not confined to the local community. At the 1995 service to mark the laying of a plaque where Stephen Lawrence was murdered, the Rt Rev Wilfred Wood, the Bishop of Croydon, said: "What is true for Stephen is also true for Roland Adams, for Rohit Duggal, for Ruhullah Aramesh, for the 13 young people who died in the New Cross fire, and for many others whose lives were taken for no other reason than that God gave them a black skin. In a society where racist murderers are forgotten after the first three or four weeks of sanctimonious commiseration, the actual murderers are only the sharp end of the chisel which is all of us."
The black television presenter Darcus Howe was one of the leaders of the New Cross march which went on from Hyde Park to Fleet Street to protest at "racist journalism".
This weekend he said the feeling on the march was that the fire had been a racist attack but he no longer wished to speculate on the cause.
A month after the march, which ended with isolated incidents of violence, the first of the Brixton riots took place.
Mr Howe said: "If it was not [the march], it could have been another issue. History had dictated that the moment was right for blacks to explode.
"The Home Office had issued a statement some weeks before, about the numbers of skirmishes taking place between blacks and the police all over London. That was the mood of the time - New Cross just happened to take place and represented the moment."
George Francis, whose 17-year-old son Jerry died in the fire, would now like the racial tension to disappear from the inquiry. He says he has not felt able to look at the three-storey house at 439 New Cross Road in the 18 years since the fire.
For four weeks after he heard news of the tragedy he was in such a state of shock that he was unable to leave his bedroom. He said: "All the parents are in limbo, not knowing what happened on that fatal night. It is a better investigation this time and we think we will get an answer. We will not forget but we will be able to rest quietly."