By Peter Gould BBC News Online

Shipman was jailed in 2000 for murdering 15 patients

The apparent suicide of Harold Shipman prompts two questions: why would he take his own life, and how could he have done it?

The second is the most pressing. The way that one of Britain's most notorious killers was apparently able to hang himself in his cell is a serious embarrassment for the Prison Service.

Shipman is not the first high-profile prisoner to contemplate death rather than face a long prison sentence. Fred West took his own life before he could be tried for the House of Horrors killings, leaving his wife, Rosemary, to face justice alone.

More recently, Ian Huntley attempted suicide while he was in prison awaiting his trial for the Soham murders. While the families of Harold Shipman's many victims may feel satisfaction at his death, some have already said that he cheated justice by taking the easy way out.

Shock and revulsion

Few cases in recent years have aroused such shock and revulsion. The fact that a trusted family doctor could kill so many of his patients was hard to believe, let alone understand.

It is a case that will live in the public's memory long after the death of Harold Shipman.

There is no question that he would have remained in prison until he died of illness or old age. The Home Secretary decided that the horrific nature of the doctor's crimes placed him in a special category of prisoners for whom life should really mean life.

One immediate question is why Shipman was not on suicide watch at Wakefield Prison. Any prisoner faced with spending the rest of his life behind bars is likely to wonder if there is any point in living.

The Moors murderer Ian Brady, another of Britain's most notorious serial killers, craves death. He has tried - unsuccessfully - to persuade the courts to allow him to starve himself to death. He remains in a secure hospital, being fed against his wishes.

Harold Shipman was no doubt thinking about his own life in custody when he decided to end it all on the eve of his 58th birthday.

Exercising power

The nature of his crimes gives us a clue about the way his mind may have been working. For decades, Shipman literally exercised the power of life and death over his patients.

Using his hypodermic syringe, he ended the lives of more than 200 of his patients, the exact number will never be known.

For the families of those Shipman killed - or is suspected of killing - his death robs them of any lingering hope of finding out exactly what happened to their loved ones.

In trying to explain why he did what he did, some have pointed to an incident in Shipman's childhood, when he had to watch his mother die a lingering death from a painful illness.

As a doctor, he acquired the power to end the lives of others, and he used that power to deadly effect. Many of his victims died suddenly at home after the doctor paid them a visit.

Little emotion

I remember Harold Shipman in court, during his trial. For day after day he sat quietly in the dock, his face betraying little emotion. He would never acknowledge his crimes, even when faced with damning evidence. After his conviction, he never showed any remorse.

Psychiatrists who examined him in prison came to the conclusion that he would never be able to talk about what he had done or why he had done it. He was unable to admit his guilt to himself, so he would never be able to acknowledge it to others. His motivation for the crimes remained locked inside his head.

Behind bars, Harold Shipman could no longer control others. Yet he still retained one power: the ability to end his life.

As the ultimate control freak, he would no doubt have taken satisfaction in choosing the exact moment of his own death.