A triple killer could spent the rest of his life behind bars after being sentenced for the murder of a "Good Samaritan" pensioner while on day release from prison.
Ian McLoughlin, 55, was given life with a minimum of 40 years at the Old Bailey after he admitted killing Graham Buck in Little Gaddesden, Hertfordshire, in July.
Mr Buck, 66, suffered fatal stab wounds when he responded to cries from the home of 86-year-old Francis Cory-Wright, a convicted paedophile, who was being robbed in the village near Berkhamsted.
McLoughlin was serving a life term for the murder of Brighton barman Peter Halls, whom he stabbed multiple times in 1992. It has prompted calls for the Ministry of Justice to explain why he was deemed safe enough to be let into the community.
He had previously been jailed for the manslaughter of Len Delgatty, 49, in 1984, whom he hit over the head with a hammer after a row, before leaving his body in a cupboard.
Mr Buck's widow Karen said "many questions still remain unanswered" about day release prisoners.
Hemel Hempstead MP Mike Penning said it was "unbelievable" on face value that a man who has committed two brutal murders could be deemed safe for day release.
He said: "Ian McLoughlin is a dangerous and violent man and should never have been out on the streets. Mr Buck and his family have paid a heavy price and we now need to know the background to the decisions that were taken so we can do everything possible to try to ensure it doesn't happen again."
Sentencing, Mr Justice Sweeney said he was barred from passing a whole life term because of a European judgment that those sentences are in breach of human rights.
The judge said: "However even for a man of 55 years of age, the minimum term of years must be a very long one indeed."
He read part of the victim impact statement from Mr Buck's widow, who sai d breaking the news of the death to her daughter was "the worst act I have ever had to carry out in my entire life".
McLoughlin met Mr Cory-Wright - who was jailed for 30 months in 2011 for indecently assaulting a 10-year old boy in the 1970s - in prison, and turned up at his house on July 13 while on day release from HMP Spring Hill, claiming to need help setting up a charity supporting elderly ex-offenders.
Father-of-three Mr Buck, who lived two doors away from Mr Cory-Wright, went to help him after hearing shouting in his front garden.
In police interview, McLoughlin said: "I'm not sorry for what I did to the nonce, but I'm sorry for what I did to the pensioner."
He said he was confronted by Mr Buck as he tried to flee Mr Cory-Wright's house, dragged him back into the kitchen and stabbed him in the neck.
Witnesses described seeing Mr Buck with his throat slashed "wide open", prosecutor Ann Evans said. He died on his front lawn, with his pet dog sitting beside him.
Mr Justice Sweeney said: "The photographs I have seen make it clear that it is no exaggeration to say that the slash was wide enough to put a fist in."
McLoughlin also admitted robbery and was given eight years to run concurrently.
The court heard details of his history of violence. When he killed Mr Delgatty, 49, he hit him over the head with a hammer several times after a row and left his body in a cupboard. McLoughlin was jailed for 10 years for manslaughter at the Old Bailey, reduced to eight years on appeal.
After his release, he went to live in Brighton, where Mr Halls, 55, offered him work.
McLoughlin said he assumed Mr Halls was gay and thought he might be expected to sleep with him.
He stabbed Mr Halls several times and had served 21 years behind bars before killing Mr Buck.
Speaking outside court after sentence, Ms Buck said: "Today has brought to a conclusion the first part of a long journey for myself and Graham's family.
"The sentence handed down by Mr Justice Sweeney today reflected the seriousness of the crimes Ian McLoughlin committed.
"However, at the end of the day, it does not change anything.
"Many questions still remain unanswered at this stage, and I await the Ministry of Justice's inquiry into day release of prisoners with interest.
"Graham's death has left a hole in many people's lives. He will be missed but he will not be forgotten."
Detective Inspector Martin Brunning added: "Forty years in prison for a man who has now been responsible for the deaths of three men over the course of the last 30 years is entirely fitting.
"It is with a degree of satisfaction that certainly Karen and Graham's wider family leave court today knowing that in all likelihood Ian McLoughlin will never leave prison, and that is a comforting factor indeed."
Justice Secretary Chris Grayling said: " It is the Government's clear view that whole life tariffs should be available for the most serious offenders.
"That is the position clearly stated in our law, and what the public expects. The domestic law on this has not changed. We are considering the Government's response to the ECtHR's (European Court of Human Rights) recent ruling, but this in no way alters that fact and courts should continue to impose whole life tariffs where they wish to do so."