The triple murderer Harry Roberts started proceedings in the High Court yesterday against the Parole Board, The Times has learnt.

The board is refusing to allow Roberts or his solicitor to see “sensitive” information and, in an unprecedented move in its hearings, it has decided that a special advocate, rather than Roberts’s lawyer, should deal with evidence linked to six specific allegations against the murderer.

The advocate would be appointed by the board and could have no contact with Roberts or his lawyers once the evidence had been seen.

Special advocates are now also being used in legal cases involving foreign terrorist suspects detained without charge. Roberts, 67, was jailed for life in 1966 after being convicted of the murder of three unarmed police officers in West London in August that year. He suspects that the decision to prevent him or his solicitor seeing the evidence is an attempt to stop him being released from jail.

Simon Creighton, a solicitor for Roberts, said yesterday: “The problems with not disclosing the material in accordance with the normal procedures go beyond the obvious unfairness of preventing our client from being able to defend himself against unknown allegations.

“If the allegations are found to be true he will be detained in prison until he addresses them. How can he address them if he does not know what they are? The genuine worry is that this procedure will mean my client might never be released from prison.”

Mr Creighton added that he had no idea of the nature of the withheld evidence. It could be linked to police intelligence collected when Roberts was allowed out of a Sudbury open prison in Derbyshire on day release in 2001. He was also allowed home leave in what was seen as preparation for his eventual release on licence.

But he was returned to a closed prison after he broke the conditions of his day release by making unauthorised journeys, including one to a leisure centre in Sheffield where he was seen celebrating his birthday with Kate Kray, the widow of the East End gangster Ronnie Kray.

Roberts, one of the longest-serving prisoners in Britain, is in Channings Wood prison near Newton Abbot, Devon. He was jailed for killing Detective Constable David Wombwell, 25, Sergeant Christopher Head, 30, and PC Geoffrey Fox, 41, who had stopped Roberts and two other men after being called to the scene of an armed robbery. The trial judge said: “This is one of those cases in which the sentence of imprisonment for life may well be treated as meaning exactly what it says.”

Roberts, who went on the run in Epping Forest for three months after the killings, is the only survivor of the incident. One accomplice, John Duddy, died in jail and the other, Jack Witney, died after he was released on licence.

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• Litvinenko murder suspect's peace offer
• Low rollers seize chance to scoop £5m on the nose
• I wish I were Chancellor now, says Ken Clarke