A man who was under 18 at the time of the Broadwater Farm riots in 1985 will be prosecuted over his involvement in one of Britain's most notorious unsolved murders.
Metropolitan Police sources disclosed that after reviewing the evidence against the man, two QCs agreed there is a realistic prospect of conviction - the hurdle which investigators must clear in order to win the backing of the Crown Prosecution Service.
Officially, Scotland Yard insisted last night that no final decision had been made and that detectives were not yet ready to bring charges.
However, senior sources said that detectives from the Met, which has kept files on Pc Blakelock's murder open for nearly 27 years, are set to charge the suspect within weeks.
The Sunday Telegraph knows the identity of the man but has decided not to disclose further details for legal and police operational reasons. It will be the first time he has faced charges in connection with the crime.
Winston Silcott and two other men were jailed for the crime in 1987 but later had their convictions quashed on the grounds they were considered unsafe.
Detectives are understood to have had their confidence buoyed by the conviction in January of Gary Dobson and David Norris for the racist murder of Stephen Lawrence.
The officers believe that if such a long standing and legally complex case can be resolved then justice can also finally be secured for Pc Blakelock.
Pc Blakelock, 40, was attacked as he tried to protect firefighters who were tackling a supermarket blaze at the height of the riot on October 6, 1985.
After stumbling, the father of three was surrounded by a mob screaming "Kill the pig".
He was stabbed dozens of times and the machete-wielding killers then tried to decapitate him. A later trial heard the mob intended to parade the constable's head on a pole to taunt other officers.
Winston Silcott, Mark Braithwaite and Engin Raghip were convicted in March 1987 of Pc Blakelock's murder but all three convictions were quashed four and a half years later, after forensic tests on pages of key interview records suggested they had been fabricated.
Silcott accepted £50,000 compensation from the Home Office but remained in prison for an unrelated murder and was released in 2003. None of the three men originally convicted is the suspect in the new case.
In 2003, Scotland Yard reopened the murder investigation after a review indicated there were possible new lines of inquiry.
It was revealed on the 25th anniversary of his murder, in October 2010, that 10 men had been arrested in London and Suffolk for questioning over the crime.
All were aged in their 40s or 50s and had lived in the Tottenham area at the time of the riot.
New forensic tests were carried out on Pc Blakelock's flame-retardant overalls, which for years had been on show to criminologists and trainee police officers at Scotland Yard's "Black Museum".
The garment and more than a dozen murder weapons - several machetes and a kitchen knife found embedded up to the hilt in the constable's neck - were analysed using updated DNA techniques for the first time.
Evidence gathered by the new inquiry is also believed to include significant new witness statements.
A Scotland Yard spokesman said at the time of the new arrests that information from witnesses had allowed detectives to "build a clearer picture of some of the events which occurred that night".
The spokesman added that detectives were seeking further people to come forward and were prepared to take "extreme measures to respect individual confidentiality" - a reference to offering "supergrasses" the opportunity to enter a witness protection programme.
Pc Blakelock's widow Elizabeth said at the time of the October 2010 arrests: "I desperately hope this leads to something. It will bring the closure that we have never been able to get.
"There's never, ever been a day goes past when I do not think of Keith and this has been hanging over us every day for the past 25 years."
Graham Melvin, 71, the detective chief superintendent in charge of the original murder investigation was later accused of fabricating a statement by Silcott, but was acquitted on all charges.
Mr Melvin said last night: "I'm delighted that the police are still very actively pursuing this dreadful crime.
"I have always hoped that those responsible for Pc Blakelock's murder would be dealt with by the courts and would get their due punishment.
"If true, then I welcome this new development."