A convicted double killer wanted for the murder of a Good Samaritan who tried to stop a robbery had a risk assessment before being given day-release from prison, it emerged today.

Police issued an all-ports alert for Ian John McCloughlin, 55, the prime suspect for the murder of retired company director Graham Buck who was fatally stabbed after responding to the frantic cries for help from his neighbour.

Police believe that Mr McLoughlin travelled from prison to rob Francis Cory-Wright, 86, a convicted paedophile who had served time in the same place as the suspect.

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Mr McLoughlin had served 22 years of a life sentence for the homophobic murder of a barman in Brighton and was being prepared for life outside prison.

Prison authorities allowed him to leave his open prison on day-release but he remains on the run after the killing inside the Mr Cory-Wright's home in the village of Little Gaddesden, Berkhamsted, Hertfordshire. Police warned that he was "extremely dangerous" and should not be approached.

Mr Buck, 66, was in his garden on Saturday afternoon when he heard shouts from Mr Cory-Wright who lived two doors away but was attacked by the intruder when he went to help. Neighbours said he was dragged into the kitchen where he was stabbed and his throat was cut.

"Mr Buck's actions were totally selfless and illustrate a deep sense of community spirit which deserves recognition and respect," said Detective Chief Superintendent Jeff Hill.

Mr Buck, who was married, had two sons, a daughter and two grandchildren, was described by his family as a man who "appreciated his life, getting great satisfaction from his family being happy and healthy".

A statement from Mr Buck's family said: "We have no words to express how much Graham will be missed. We were all in such a happy place as a family. We were all so settled, with growing numbers of grandchildren whom he adored being around.

"We haven't seen him happier than being around his grandchildren whom he adored being around. We haven't seen him happier than being around his grandchildren, he was so proud. We cannot get over that we have lost him. He's going to be missed by so many people."

The prison authorities were yesterday examining the circumstances of Mr McLoughlin's release from prison. He was due to return to Spring Hill open prison, in Buckinghamshire, at 7pm on Saturday after securing the concession for undisclosed reasons.

Before a life prisoner can be let out on day release, he must have spent time at an open prison and taken out on escorted visits. The inmate most provide reasons for being let out on day release and a risk assessment is then carried out, said the Ministry of Justice.

Police said that Mr McLoughlin, a heavy drinker who had a previous conviction for the manslaughter of another man in 1983, was motivated only by money in heading to Mr Cory-Wright's home. He was said to have left the house with bundles of cash and caught a taxi to Watford.

Mr Cory-Wright was jailed for 30 months in 2011 for indecently assaulting a 10-year old boy in the 1970s. He was said to be in poor health but was treated in hospital after the attack, but has since been discharged.