Police have warned the public not to approach an escaped murderer who could be in Portsmouth.
Officers have made a new appeal for help to find Robert Donovan, 57.
He was jailed after he stabbed to death a man in the street in London’s West End when he was 17. In December 1974 he was jailed for life for the murder.
He was later moved to Ford Prison near Arundel and left there on day release on June 19, 2010. He did not return and officers have been unable to trace him since.
A Sussex Police spokesman said the force had exhausted all lines of inquiry during the intervening four years and now needed the public’s help.
Police say Donovan, who could be using the alias David Green, has links to London and the West Midlands and may have family living in Portsmouth.
PC Steve Reed said: “We have been looking for Donovan for several years without success which suggests he has left Sussex and could be elsewhere in the country.”
He said there was nothing to indicate Donovan was a danger to the public, but he should not be approached.
Officers advise that anyone seeing him should call 999 or call 101 quoting his name.