Harold Shipman is the third serial killer to have been found hanging in his cell in the last decade.
Many inmates cannot "do the time"
On New Year's Day 1995 Gloucester builder Fred West was found dead in his cell in Birmingham's Winson Green prison, where he was being held pending his trial on 12 murder charges.
West was on suicide watch - which meant he had to be checked on every 15 minutes - but he chose his timing perfectly and by the time he was found he was already dead.
It was widely thought that West hoped his own death would make it harder for his wife, Rose, to be convicted of the murders. But in the event she was jailed for life 11 months later.
In August 1999 Stephen Akinmurele, 21, was found dead in his cell at HMP Manchester, formerly known as Strangeways.
West may have been trying to protect his wife
Akinmurele was on remand awaiting trial for the murder of three pensioners in Blackpool. He was also suspected of several murders on the Isle of Man.
Now Shipman, serving 15 life terms, has been found dead in his cell in Wakefield prison, West Yorkshire.
Shipman was not under suicide watch and had not been on suicide watch since his arrival at Wakefield in June.
David Ramsbotham, former head of the Prison Service, said it was difficult to assess the mental state of prisoners facing life sentences.
He told BBC News 24: "If people have got something to aim at and you can give them a target, which is naturally going to be their release provided they do what's required of them, then perhaps you can give them some purpose in life.
"But somebody who's not going to get out may lack that purpose and therefore it must be very, very difficult to be precise about their mental state - certainly more than about someone who's going to get out.
Ironically, an inquest in May 2001 heard how Shipman had tried to talk a cell mate out of killing himself.
Peter Hall, 35, from Bolton, Greater Manchester, was serving life for murdering his girlfriend, Celeste Bates, and her two sons, Daniel, eight, and Milo, 17 months.
Shipman offered Hall "friendly advice" on how to overcome his remorse when the pair were on remand in Strangeways.
However, two months after Hall was transferred to Wakefield, in October 1999, he was found hanging in his cell.
Simon Meyerson, a consultant psychologist, said Shipman may have killed himself because the "wall" protecting him from his own guilt may have disintegrated.
Mr Meyerson said many psychotic serial killers suffered from what is known as the "schizoid split", which means they tell themselves they are either innocent or were acting for good reasons.
When this split breaks down, they are left to face the enormity of their actions, and this can leave them feeling suicidal.
Mr Meyerson told BBC News 24: "If you are living on one side of the split then everything is OK. You're feeling OK, you're telling yourself a good story every day.
Stephen Akinmurele killed himself in jail in 1999
"But if the wall between the two sides starts to disintegrate then the guilt can seep through and the risk of suicide becomes quite high."
He said he believed the prison authorities' recent decision to strip Shipman of his privileges at Wakefield because of poor behaviour may have played a big part in his death.
"When his rights were removed a lot of his grandiosity was knocked out, and alone in his cell without a television, he had to come to terms with what was trying to get into his conscious mind," he said.
Only last week, the Howard League for Penal Reform pointed out five people had killed themselves in West Yorkshire prisons last year.
Three of them were female inmates at New Hall Prison, near Wakefield.
The Howard League's director, Frances Crook, said on Tuesday: "If only serious and violent offenders who were a danger to the community were held in prison they could be monitored and managed safely with sufficient numbers of skilled staff."
Marjorie Wallace, the chief executive of mental health charity Sane, said: "The death of Harold Shipman exposes what we already know, that the prison psychiatric services are threadbare and unable to supervise either those with known mental illness or a history of suicide attempts."