On Christopher Pailthorpe's final journey, from London to Zurich, his “physical pain and mental anguish grew with every mile travelled”. His friend and companion noted the irony of the situation: the journey was the result of Mr Pailthorpe's quest for a painless and dignified end to a life that he could no longer bear because of advanced cancer. Was it a journey that British law should have spared him?

The same question is posed by two other cases, both deeply distressing, that have brought only confusion from the legal system where it should bring clarity.

In one, Debbie Purdy, confined to a wheelchair since 2001 because of multiple sclerosis, has demanded to know whether her husband will be prosecuted if he helps her to travel to Switzerland to end her life. The High Court has reserved judgment. In the other case, the parents of a rugby player paralysed in a training accident accompanied him to Zurich to help him to commit suicide, knowing they might face prosecution on their return. The Director of Public Prosecutions is deciding whether to press charges.

Assisted suicide is illegal in Britain on the basis that those contemplating suicide are vulnerable, and the vulnerable deserve the law's protection - whether from unscrupulous or unfeeling relatives or doctors, or their own depression. Parliament has debated long and hard opposing arguments that the terminally ill should be allowed more control over the time and manner of their death. So far, it has rejected them. Meanwhile, in Switzerland, Belgium, the Netherlands and Oregon, assisted suicide for the terminally ill is legal.

Zurich in particular has acquired an unwonted reputation as Europe's “death tourism” capital. Roughly 100 Britons have travelled there to end their lives with the help of the Dignitas organisation alone. Some 650 more are Dignitas members, paying annual fees to guarantee them a place to die and a fatal dose of sodium pentobarbital when their illness becomes intolerable.

The availability of legal assisted suicide elsewhere does not affect the moral arguments for or against it. But it does affect how the Government should respond to them. As Baroness Warnock has cautioned, by acquiescing to British use of Swiss suicide clinics without changing its own laws, Britain is drifting towards a “two-tier death service”. Those who can afford the journey and the fees retain an independence in death that those who cannot must cede to the NHS and the hospice movement; their only alternative, if they want to end their own lives, is to seek help from those willing to break the law.

Despite its name, and its protection under a 67-year-old Swiss law, Dignitas operates in quasi-guerrilla fashion (see page 32). As neighbours count the body bags and lodge complaints, it continues to rent flat after flat. Hundreds have chosen to use them nonetheless. A Bill sponsored by Lord Joffe would have allowed those Britons among them to die at home, without exorbitant expense. It was defeated in 2006 after passionate debate in which opponents of assisted suicide freely and understandably invoked the sanctity of life. Subsequent events suggest they may not have paid enough heed to the requirements for dignity in death.

Just as Ms Purdy deserves clarity from the law, Lord Joffe's Bill deserves another reading.