Police have appealed for help in tracing a "potentially dangerous" murderer who went on the run after escaping from Pentonville Prison.

John Massey, 64, made off from the jail in Islington, North London at around 6.30pm yesterday.

The convicted killer was sentenced to life imprisonment for the murder of a man at a pub in Hackney, East London in 1975.

It has not been revealed how Massey escaped from Pentonville, but an investigation into how he managed to elude staff is due to be launched by the the Prison Service.

A Prison Service spokesperson said: "At approximately 6.30pm on Wednesday 27 June a prisoner was found to be missing from HMP Pentonville. Police were immediately informed and the matter will be the subject of a thorough investigation."

Scotland Yard have advised members of the public not to approach the "potentially dangerous" offender and instead call 999 if he is spotted.

Pentonville houses up to 1,250 category B and C male prisoners, rather than the most serious category A offenders.