The release of Britain’s longest-serving prisoner dubbed the Devil’s Disciple has been postponed indefinitely as police probe eight more killings linked to him.

Patrick Mackay, 67, has been behind bars for 45 years since his manslaughter convictions at the Old Bailey in 1975 for strangling two elderly women and butchering a priest with an axe.

The Parole Board were due to decide whether Mackay was safe to be let out after his move to an open prison.

But the Nazi-loving psychopath had originally confessed to eight more victims during a killing spree in London, Kent and Essex in 1974-75.

Now Gareth Johnson, Tory MP for Mackay’s home town of Dartford, Kent, has persuaded Essex police to investigate the cases.

Mackay was 23 when he was convicted of the manslaughter due to diminished responsibility of Father Anthony Crean, 63, (picture) Isabella Griffiths, 87, Adele Price, 89.

Mr Johnson, who was contacted by the son of one of the victims to express his fear the killer may walk the streets again, said: “These other crimes must be fully investigated before he is considered for release.”

Mackay was 23 when he was convicted of the manslaughter due to diminished responsibility of Father Anthony Crean, 63, Isabella Griffiths, 87, Adele Price, 89.

Two of the other eight killings were left on file and Mackay retracted his confession to six.