An anti-paedophile vigilante who murdered a gay man he wrongly believed to be a child molester has been told he may never be released from prison.
Christopher Hunnisett, 28, killed Peter Bick, 57, just four months after being freed from jail following his acquittal for a vicar's murder.
He was jailed for life with a minimum term of 18 years at Woolwich crown court in south-east London on Tuesday.
But the judge, Mr Justice Saunders, warned he was an "extremely dangerous man" who "may well kill again" if released in the foreseeable future.
The judge said: "The time may never come when this defendant is considered safe to be released."
Hunnisett had previously spent more than nine years in jail for killing the Rev Ronald Glazebrook, 81, in his bath and cutting up his body in April 2001.
But his conviction was quashed and he was cleared of Glazebrook's murder at a retrial during which he alleged that the priest sexually abused him.
After being freed from prison in September 2010, Hunnisett, of Hastings, East Sussex, made a "hit list" of men he planned to kill in an effort to rid the world of paedophiles.
Having formulated a plan to track down child abusers and rapists while he was in custody, on his release he set up false internet accounts as a "honeytrap" for sex offenders.
Bick, an Asda employee from Bexhill-on-Sea, East Sussex, was at the top of Hunnisett's list of targets, although the prosecution said there was "not a shred of evidence" that he was a paedophile.
Having split up from his long-term partner, the supermarket worker regularly used social networking and dating websites to meet young men for consensual sex, the trial heard.
Overnight on 10-11 January last year, Hunnisett had sex with Bick at his flat before brutally smashing his head with five severe hammer blows and strangling him with a shoelace.
The killer tried to cover his tracks by sending text messages falsely suggesting Bick believed he was meeting a 15-year-old boy.
Saunders said Hunnisett went to Bick's flat prepared to kill him, and carried out a "planned and cold-blooded" attack.
He noted that the defendant had an "intense hatred" of paedophiles, having suffered abuse as a child.
The judge said: "He believes that the penalties handed out by the courts for child abuse are inadequate.
"For him the appropriate penalty, if he considers it necessary, is death. He has appointed himself judge, jury and executioner.
"However good the evidence of child abuse, the defendant was not entitled to take the law into his hands in the way he did but, as he demonstrated in this case, he was prepared to reach his conclusions on entirely inadequate evidence."
Saunders observed that Hunnisett's hatred of paedophiles grew during his time in prison, where he might have come into contact with sex offenders who showed a lack of remorse for the harm they had caused.
He said: "The evidence that I have heard has driven me to the conclusion that the defendant is now an extremely dangerous man who may well kill again were he to be released in the foreseeable future.
"The parole board will undoubtedly take all that into account when deciding when, and if, this defendant should ever be released."
David Martin-Sperry, mitigating, said that while in prison Hunnisett was forced to play the role of an abuse victim in therapy sessions organised for sex offenders.
He was then freed after being acquitted of Glazebrook's murder without being prepared for his release and with no authority responsible for supervising him in the community.
Hunnisett, unshaven in a black and grey casual jacket, made no reaction as his sentence was passed, but mouthed a few words to family members in the public gallery as he was led away by court guards.
Following the case, Detective Chief Inspector Nick Sloan of the Surrey and Sussex major crime team said: "This was a terrible crime, and the jury were clearly unconvinced by Hunnisett's claims about his motives for carrying out such a cruel and deliberate killing.
"Peter Bick's sister, together with her husband, was present at court throughout the trial and they had to listen to Christopher Hunnisett deliver utterly unfounded personal attacks about the character of her brother.
"They endured this with great dignity and this is testimony to how they have conducted themselves since Peter was murdered.
"What exactly was motivating Hunnisett in the lead up to the murder and afterwards we will perhaps never really know, but there is no doubt at all that society is a safer place now that he is in prison."