Police killer Harry Roberts is to be released from prison after serving more than 45 years behind bars.
He was jailed for life for the murder of three policemen in Shepherdâ€™s Bush, west London, in 1966 and told he would never be released.
Chair of the Police Federation of England and Wales, Steve White says he is appalled at the decision.
â€œLetâ€™s not forget, this menace murdered three unarmed police officers in cold blood and it is abhorrent news,â€ he said.
â€œThis decision by the parole board is a slap in the face for the families of the three police officers he brutally murdered who, once again, are forced to re-live their pain and loss. It will spark fury among everyone in the police family who will feel badly let down.
The officers were shot, in what was later called the massacre of Braybrook Street, after they pulled over
a van containing Roberts and two others.
PC Geoffrey Fox, 41, Sergeant Christopher Head, 30, and Detective Constable David Wombwell, 25, had approached the van after seeing it parked near Wormwood Scrubs prison.
The officers were in plain clothes and had approached the van after suspecting a prison break. In fact the men were preparing to commit an armed robbery.
Roberts shot dead Mr Wombwell and Mr Head, while Mr Fox was killed by another member of the gang.
Roberts was given three life sentences for the murders and his 30 year minimum tariff expired 18 years ago.
When he was finally brought to justice, Mr Justice Glyn-Jones said it was a â€œheinousâ€ crime and told him: â€œI think it likely that no Home Secretary regarding the enormity of your crime will ever think fit to show mercy by releasing you on licence.â€
He would have faced the death penalty but it was abolished eight months prior to his sentence.
The 78-year-old has now been approved for release by the Parole Board.