One has to greatly admire Debbie Purdy's persistence in going through the British legal system in order to protect her husband if, when she becomes terminally ill (ie. likely to die within six months), he accompanies her to the Dignitas clinic in Zurich should she choose an assisted suicide.

Now suffering from multiple sclerosis for several years, and in a wheelchair since 2001, Debbie, 45, from Bradford, lost her Appeal Court case yesterday.

She had been hoping to get greater clarification on the present law regarding assisted suicide. Under the 1961 Suicide Act, which decriminalised suicide in England and Wales (it did not apply to Scotland because, in strictly legal terms, suicide was never a crime there!), if someone aids, abets, counsels or procures the suicide of another, that person could be jailed for up to 14 years. And, Debbie Purdy wants to protect her husband from that possibility.

The Appeal Court judges said that the Director of Public Prosecutions (DPP) could not adopt a "case-specific policy in the kind of certain terms sought by Ms. Purdy"; that it had to be Parliament which decided if the law should change; but, in what was a rather surprising comment, they added that even if a defendant in an assisted suicide case were to be convicted, a court could decide that no sanction was appropriate. That last compassionate statement seems, in my view, to have justified all that Debbie has been striving to achieve.

During the past decade, at least 100 individuals have travelled from the UK to Switzerland for an assisted suicide. While several relatives or close friends, upon their return to Britain, have been questioned by the police about what happened, no one has yet been prosecuted. And, it is important to note that not all those who have ended their lives in Switzerland were terminally ill - such as Daniel James who died in the Dignitas clinic last September (he had been severely paralysed following a rugby scrum injury eighteen months earlier).

Obviously, in a strictly legal sense, it is a crime to assist someone to go to Switzerland for an assisted suicide. I have a Home Office letter, written to a friend of mine in February 2007, which says "In our view, though the point is untested in the courts, an offence (under the Suicide Act) is committed even where the suicide occurs abroad if the aiding, abetting etc. takes place in this country". This letter adds that it is up to the DPP to decide whether or not to prosecute in individual cases, "taking into account all the circumstances including the public interest in bringing a prosecution". But, surely if a law is not enforced fairly and often, it will eventually become a non-law?

I am certain that Debbie Purdy's husband, Omar Puente, has nothing to fear if, one day, they travel together to Zurich, to Dignitas. In the past three years, I have accompanied three terminally-ill individuals from the UK to Switzerland, and witnessed their dignified and peaceful assisted suicides there, with the help of Dignitas. I have been interviewed by the police about these trips, and reports have been sent to the DPP - but nothing further has happened. Therefore, as I was not even related to any of those I helped, I am sure that Omar Puente, acting as a dutiful husband - and most unlikely to repeat his "crime" - will not have any problem, from the police, upon his return.

If Debbie Purdy wants further support, I am prepared to travel with her and her husband when they go to Zurich. Other campaigners who seek to change the law may also want to accompany her? Perhaps there is "safety in numbers"? For my first trip to Zurich, seven people helped the terminally-ill lady to make the journey. On my last trip, four were involved. The DPP is most unlikely to want to put a crowd in the dock.

Today, legalised doctor-assisted suicide, with very adequate safeguards, is possible in Belgium, The Netherlands, Switzerland, and the American states of Oregon and Washington. The law should be changed in the UK (80 per cent of the public wants this to happen). Are we, in this country, so different from the Belgians, the Dutch, the Swiss, or those who live in Oregon or Washington State?

Michael Irwin is former chairman of Dignity in Dying