BRITAIN'S most notorious police killer won a battle yesterday to force David Blunkett to release a secret report blocking his attempt to win parole.

Hours before the start of a High Court hearing, the Home Secretary agreed that lawyers for Harry Roberts, serving life for the murder of three police officers in 1966, may see a dossier of evidence sent to the Parole Board.

Mr Blunkett's change of heart could hasten the release of Roberts, 66, who is one of Britain's longest-serving prisoners. He is now a category C inmate at Channings Wood in South Devon.

The dossier is believed to have covered Roberts's activities last year when he was on day release from open prison. He was alleged to have been seen in London with criminals when he was supposed to be working at an animal sanctuary. He had also been taking driving lessons, which he was not allowed to do.

Roberts was moved to a closed prison, but applied for parole. In May his lawyers learnt of the dossier and the Parole Board decided that they should see the evidence against him. The Home Office diagreed and the action was launched with Roberts's lawyers arguing that there was no other process where someone could be deprived of liberty on the basis of secret material.

Mr Justice Sullivan was told that the Home Office and lawyers for Roberts had agreed that the Parole Board should decide what to do with the dossier. It will be seen by a lawyer for Roberts or, if it was considered very sensitive, it might be read by a specially appointed and vetted independent lawyer chosen to act for Roberts.

Simon Creighton, Roberts's solicitor, said that the Home Office position had delayed a parole hearing for months. It could now be heard before the end of this year or early next year. He said that Roberts denied any wrongdoing while in prison, but until the allegations were known it was difficult to refute them.

Roberts is the last living member of the gang involved in the Shepherds Bush shootings in West London. Three police officers stopped a van carrying Roberts, John Duddy and Jack Witney, as they fled from an armed robbery. Roberts shot Detective Constable David Wombwell dead at point-blank range. He then turned the gun on Sergeant Chris Head, shooting him in the back. Duddy then shot dead PC Geoffrey Fox.

Duddy and Witney were arrested quickly, but Roberts went on the run for three months. At an Old Bailey trial, Mr Justice Glynnes sentenced Roberts to a minimum of 30 years. His criminal record includes a seven-year term for beating a man so badly that he later died. He tried to escape 22 times and was refused parole in 1996.

Witney was murdered in a hostel and Duddy died in jail.