IT was his driving that gave him away. Joan Wilkinson remembers noticing the first signs of Parkinson's Disease in her husband Arthur when he was behind the wheel of his car.

"As he was driving along he couldn't hold his foot down on the accelerator. That was the first sign that there was anything wrong," says Joan, who has cared for her husband since he was diagnosed with Parkinson's Disease 28 years ago. "His writing suffered as well," she remembers. "He would start to write a sentence and his handwriting would get smaller and smaller."

Since the first diagnosis, her husband's condition has steadily deteriorated. Now Arthur, 78, is in a wheelchair and can only just feed himself. Despite the cruel and random nature of a disease that is progressively degenerative, the couple still count themselves relatively lucky. "About half of Parkinson's Disease patients develop dementia, but Arthur is still pretty good. He takes an interest in life, he enjoys music and watching television," says Joan, 69.

There is no cure for Parkinson's Disease but some of the worst symptoms, such as shaking, can be controlled by medication. Unfortunately, the drugs often produce unpleasant side effects. "The treatment we have now makes my husband sick. Sometimes his limbs twist of their own accord and he can't stop them," adds Joan.

While Joan is philosophical about her own family's situation, she is delighted about last night's decision to allow further research into the use of embryonic stem cells, which holds out the prospect of a potential cure. This summer, an expert group chaired by the Chief Medical Officer Professor Laim Donaldson reviewed the potential for developments in stem cell research to benefit human health. It concluded that stem cells "offer tremendous potential for the development of revolutionary forms of medical treatment for serious injuries or debilitating diseases." Research aimed at studying how stem cells behave could lead to them being a new source of tissue to repair or replace damaged parts of the body. This could be after someone has suffered burns or as a treatment for diseases such as hepatitis, diabetes, leukaemia or Parkinson's Disease.

While there are a number of sources of stem cells - which have the ability to develop into different kinds of tissue within the body - it is stem cells from human embryos up to 14 days old which are the most promising and have generated the fiercest controversy. On one side of the divide are scientists who say these pin head-sized balls of around 100 human cells, produced as a by-product of test tube baby treatment and currently discarded in their hundreds of thousands, only have the potential for human life. On the other side, religious groups and pro-Life campaigners say that all embryonic cells should be protected and it is immoral and dehumanising to create and then destroy human life in this way.

Joan Wilkinson had never heard of stem cells until a few years ago, but now she believes they hold the promise of a miracle treatment for people like her husband. "It's a bit late for my husband, but I believe that this will help other Parkinson's Disease sufferers in the future," she says.

Joan has been the Durham branch secretary of the Parkinson's Disease Society for 14 years. Recently, she has been enthusiastically campaigning in favour of stem cell research. The Parkinson's Disease Society says the best hope of finding a cure is through stem cell research.

Last night's vote "paves the way for vital research that gives people with Parkinson's Disease the chance of a better future," says Robert Meadowcroft, PDS Director of Policy. Joan agrees: "There are 120,000 people with Parkinson's and at least another 120,000 carers. There is no cure at the moment and stem cell research seems to be a possible way forward. I do think we deserve some consideration as well."

The PDS has been at the forefront of the campaign to allow more research and last night's vote by MPs was the culmination of four months of lobbying by the organisation. Simon Hope, press officer for the PDS, freely admits that there is no guarantee that stem cell research will lead to a breakthrough. But all the research so far points to a potential health bonanza, with scientists eventually able to grow a wide range of human tissue, including cells which produce dopamine, the absence of which leads to the shaking, stiffness and slowness of movement known as Parkinson's Disease.

Mr Hope says: "It is like Catch 22. You don't know until you do the research. If we can find stem cells which produce dopamine, which is a chemical messenger which helps us to co-ordinate our movements, you could either reverse the symptoms of Parkinson's Disease or even find a cure." Last night's vote was "very important", he adds. "The next hurdle is getting this through the House of Lords."

Although the relaxation of rules is supported by the Government, it is customary to allow MPs and peers a free vote over matters of conscience. Another supporter of stem cell research is Professor John Burn from Newcastle University, who sat on Prof Donaldson's committee. He has no doubt that the legalisation of embryo stem research represents an important step forward.

"We have already had three broad-based committees look at this issue, not just scientists and doctors but theologians as well. They are saying that when you take the facts together stem cell research has enormous potential," he says.

Prof Burn, who is medical director of the Institute of Medical Genetics in Newcastle and one of the top genetics experts in the UK, said as far as he could see there was no new ethical issue involved in extending the scope of our existing research into human embryo cells, produced after sperm and eggs are mixed.

"We have already accepted that we can look at very early fertilised eggs to achieve test tube babies. This is not so very different." He says it is important to remember the argument that life begins at the moment that the human egg is fertilised is not accepted by most of the world's major religions.

"Provided you do not do anything beyond 14 days of pregnancy, which is when the embryo proper starts to form, most of the cells will just turn into the placenta," says Prof Burn. "Most of those cells have the potential to be anything. They have not yet decided what they are going to be and that is why they are so precious."

Virtually any disease might be treatable in the long-term if stem cell research delivers the goods. If the vote had gone against stem cell research, Prof Burn feared that the work would continue in the private sector outside Britain. If we had gone down that road it is likely that any resultant treatment produced commercially would be so prohibitively expensive that it would be beyond the reach of most people who needed it. Prof Burn says that is also an ethical question that must be set against the religious arguments for halting research into human embryos.

Joan Wilkinson just hopes it all has a happy ending. "When you have lived with someone with Parkinson's Disease for so long you know how important it is to search for a cure. This seems to be our best bet," she says.