The initiative is partly in response to a recommendation in the Lawrence inquiry report.
John Stevens, the Deputy Commissioner of the Metropolitan Police, announced yesterday that teams of detectives and forensic scientists will use new DNA techniques to recover clues previously missed from unsolved killings or cases that have gone "cold" in the London region. They will also re- examine witness statements.
Murder squad detectives will trawl back to 1984 when details of killings were first recorded on computer. "Cold cases" will be reviewed every two years for possible break-throughs.
In a separate development, from next month all unsolved murders will be reviewed every month by three specialist units staffed by 44 detectives to ensure they are making progress.
The Metropolitan Police fails to catch murderers in about 10 cases out of 100, on average, each year. Last year the murder toll was exceptionally high, with about 180 in the capital. Since 1988 there have been about 300 murders that remain unsolved.
The decision to re-examine the killing of PC Blakelock was prompted by an appeal to Sir Paul Condon, the Metropolitan Police Commissioner, from the dead man's widow, Elizabeth Johnson. PC Blakelock was murdered in October 1985 on the Broadwater Farm Estate in Tottenham, north London by a mob armed with knives and machetes. Mrs Johnson said: "I haven't given up hope that they will catch Keith's killers. If Sir Paul has pledged to do everything he can to bring Stephen Lawrence's killers to justice then why can't he do the same for Keith?"
She added: "I have never blamed the police for not bringing his killers to justice. I blame the black community for not coming forward. They know who murdered my husband and they've got to remember racism is a double edged sword."
Winston Silcott was convicted of the policeman's murder in 1987 but was acquitted in 1991 after new evidence showed that police notes of an interview had been altered. A second investigation into the murder in 1994 failed to bring any convictions.
The murder of Rachel Nickell, who was sexually assaulted and killed in front of her two-year-old son in 1992, will also be reviewed. Original inquiries in the case led to the trial of Colin Stagg in 1994. The judge halted proceedings and entered a not-guilty verdict after ruling that evidence gathered by an undercover officer was inadmissible.
It was also announced yesterday that the Met will introduce measures to cut the number of accidents involving police cars by 10 per cent after it was discovered that half the collisions during emergency calls are the fault of the police.
Last year six people died, including one officer, 94 were seriously injured - 51 were officers - and 1,538 people were slightly hurt during police accidents. To reduce the number of accidents, cars are to be fitting with aircraft style "black boxes" that will record the actions of the driver.
t Sir Paul Condon has left hospital and is recovering at home after suffering severe food poisoning. He is expected to return to duty in about three weeks.
Rachel Nickell was sexually assaulted and stabbed to death in front of her two-year-old son on Wimbledon Common, south-west London, in July 1992.
PC PATRICK DUNNE
PC Dunne was shot in 1993 while investigating a minor disturbance in Clapham, south London. Three men arrested and charged but case was dropped by the CPS.
MICHAEL McCORMACK AND JOHN OGDEN
Two businessmen, Michael McCormack and John Ogden, were shot dead as they walked to work in Balham, south London, in 1994. Police believed that the men may have been murdered by mistake in a gang warfare `hit'.
Ronald Hinkson, 32, died after being stabbed 10 times during a brawl outside a bar in Camden, north London, in September 1997.
PC KEITH BLAKELOCK
PC Blakelock was hacked to death after being assaulted by a mob during riots in October 1985 on the Broadwater Farm Estate in Tottenham, north London.
Brandon Hale, 48, was shot dead in a gangland-style killing and his body was dumped in Queens Wood, Highgate, north London, in January 1997.
Hannah Deterville, 15, was stabbed more than 20 times before being dumped in woodland at Greenford, west London, in January 1998.
Katerina Koneva, 12, the daughter of a Macedonian refugee, was strangled at her home in Hammersmith, west London in May 1997.
SUSAN BLATCHFORD AND GARY HANLON
Susan, 11, and Gary, 13, were found in a shallow grave in 1970. The "Babes in the Wood" case hasrecently been reopened.