Legal challenges in this country and to the European Court of Human Rights have altered the sentencing guidelines for Britain's worst murderers in recent years.

In November 2002, the Law Lords upheld the case of Anthony Anderson, a murderer who kicked two men to death. He argued that under the European Convention on Human Rights, the Home Secretary should not have the right to extend his sentence without a judge's approval.

The Anderson case gave judges, rather than politicians, the power to set the "tariff" - the minimum sentence a prisoner must serve before he is considered for parole - and allowed more than 200 killers, whose punishments were amended by the Home Secretary, to have their sentences reviewed by the courts.

But in 2003, the setting of tariffs for Britain's most dangerous murderers was updated again. This time by the Criminal Justice Act 2003, which spelt out the types of cases in which killers could be sentenced by judges to "whole life tariffs" under which they would die in prison.

Under the law, whole life tariffs can be set in cases of "multiple murders that show a substantial degree of premeditation, involve abduction of the victim prior to the killing or are sexual or sadistic" and in cases where a child is murdered after being abducted.

The transfer of sentencing powers from the Home Secretary to the High Court and now, under the Criminal Justice Act, to trial judges, has prompted some of Britain's longest-serving murderers to try and have their punishments reviewed.

In December 2002, when the powers were formally "in transition", John Straffen, Britain's longest serving prisoner, tried to challenge his whole-life sentence in the Court of Appeal. Straffen, now 75, murdered two young girls in Bath in 1951. He then escaped from Broadmoor for three hours in 1952 and killed another girl before he was captured. Straffen's appeal was turned down.

According to the Home Office, which refuses to confirm the individual identities of inmates, there are 28 prisoners currently serving whole life sentences, including two, David Bieber and Mark Hobson, who were given their punishments by the courts in 2004 and 2005 respectively.

Four of Britain's worst:

Abused as a boy, Robert Maudsley was imprisoned in 1971 after working as a rent boy and murdering one his clients. Declared unfit to stand trial, he was locked up in Broadmoor where, with another inmate, he took a prisoner captive and tortured him for nine hours before cutting the top of his head off. Then sent to Wakefield Prison, where he killed two more inmates. Has been in solitary confinement since 1979.

Donald Neilson was nicknamed "the Black Panther" when police were hunting for the killer of three postmen and a security guard in the early 1970s. Neilson wore distinctive combat fatigues when he broke into post offices and murdered their staff. His fifth victim was Lesley Whittle, a 17-year-old heiress who he kidnapped and left to die in a drain.

Dennis Nilsen admitted murdering at least 13 men in 1983. He worked as a civil servant, but over the course of four years lured more than a dozen men back his flat where they would have sex and he would kill them. Nilsen hit the bodies under his floorboards and burned them later in the garden.

Colin Ireland was jailed in 1993 after murdering five gay men in bid to become a serial killer. He is believed to have been desperate to kill six people to earn the official designation. Fortunately he had to settle for "mass murderer" but some believe he would have stopped killing when he reached six.

These killers are also among the 28 whole lifers

Ian Brady, 1966. The Moors Murderer.

Harry Roberts, 1966. Shot dead three policemen during a robbery.

Dennis Stafford, 1967. Murdered a fruit machine cashier. Jailed again after further offences

John Hilton, 1978. Killed two men within months of release.

Peter Sutcliffe, 1981. The Yorkshire Ripper, 13 murders.

Arthur Hutchinson, 1983. Gatecrashed wedding reception, killed bride's parents and their son

Jeremy Bamber, 1986. Shot dead adoptive parents, sister and her two children

John Duffy, 1988. Double murderer, rapist

Kenneth Erskine, 1988. The Stockwell Strangler, seven murders

Victor Miller, 1988. Murdered teenage boy

Beverly Allitt, 1993. Murdered four children

Robert Black, 1994. Murdered three schoolgirls

Rosemary West, 1995. Ten murders

Peter Moore, 1996. Jailed for killing four men, tortured more than 50

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