The 40-year-old officer was killed during the Broadwater Farm riot in Tottenham, north London, in October 1985. He died as he tried to protect firemen dealing with a blaze started by the rioters on the council estate.

PC Blakelock's case is being given top priority

The killers have never been brought to justice.

In 1987 three men - Winston Silcott, Mark Braithwaite and Engin Raghip - were convicted of PC Blakelock's murder, but the convictions were quashed on appeal.

Silcott, who is currently serving life for another murder, is suing the Metropolitan Police for malicious prosecution.

The case will be heard at the High Court in June 2000.

New methods of forensic science, including DNA testing, and changes in the status of crucial relationships are some of the angles which will be covered by the review.

The review is expected to take several weeks.

Metropolitan Police Deputy Commissioner John Stevens visited PC Blakelock's widow at her home near Newcastle last week to discuss the case.

No new re-investigation

A spokesman said he assured Elizabeth Johnson that the case was to be given top priority by one of the independent review teams which have been established within the Metropolitan force.

But Scotland Yard emphasised that the review of the case did not constitute a re-investigation.

It said: "A full and thorough re-investigation was carried out by Commander Perry Nove between 1992 and 1994, and the evidence produced was carefully reviewed by leading Treasury Counsel.

"The Crown Prosecution Service decided that there was insufficient evidence at that stage to provide a realistic prospect of conviction."