'The reason I chose homeopathy over other complementary therapies is that it treats the whole individual and stimulates the body's own healing mechanisms. It is based on the Hippocratic Law of Similars, and one way of understanding it is as an advanced form of vaccination based on the premise that something that is capable of producing a disease is also capable of preventing it or stimulating the body's defences to deal with it. Homeopathy is based on empirical knowledge and is founded on more than 200 years of clinical implementation and trials. We just work with what has worked before in the same circumstances.'

Homeopathy began with Samuel Hahnemann, a conventional German doctor working in the 1780s, who took a step back from contemporary medicine, contemplated the universal application of bleeding, leeches and emetics and concluded, not unreasonably, that what this was mostly doing was reducing the body's ability to resist disease, not increasing it. His solution was to move away from the established practice of healing by introducing new substances to the body, which the disease cannot resist (aleopathy: effect through opposites), and instead introduces in minute quantities a substance that can cause the condition (homeopathy: effect through similars).

Both systems, as Dr Hahnemann saw it, had been advocated by the founding father of medicine, Hippocrates, but homeopathy had somehow been abandoned and ultimately forgotten along the way. Experimenting extensively and in the time-honoured manner using himself as principal guinea pig, he effectively established homeopathy as the practice we know today following three fundamental principles:

A substance that in large doses causes the symptoms of a disease will, in small doses, cure that disease.

Extreme dilution enhances a remedy's therapeutic properties while eliminating toxic side effects.

Homeopathic diagnosis also requites a proper study of the patient's psychology and emotional condition.

As to what substances are used to create homeopathic remedies, Mr Glencross is quick to dispel the illusion that only organic products are used. 'Homeopathy uses whatever is proven to work in practice. In some cases that means plants, but we also use gold and other heavy metals, cobra and rattlesnake venom, nux vomica (the strychnine tree), belladonna and numerous other substances that in any significant quantity would do you no good at all. Remember the principle is to use a substance that can provoke the symptoms of a disease, only in extremely diluted quantities.'

It is the extent of this dilution that elicits the contempt of conventional clinical medicine. Homeopaths claim that proper clinical testing, including double-blind crossover tests, have been carried out successfully. Homeopathy's many opponents contest that the tests have been error-strewn and impossible to reproduce. The most contentious of homeopathy's claims is that the solutions used in remedies are effective but non-toxic because they are diluted to the extent that all that remains of the substance used is a 'memory' in the water prescribed. Conventional science has, however, yet to be persuades that water possesses the power of memory.

What remains is a conflict between those who believe that the power of homeopathy lies entirely in the placebo effect and those who believe in its objective effectiveness in preventing and curing disease, including Mr Glencross, who took the placebo issue by the horns and examined the successful effects of homeopathic remedies on pets - who even the most grudging clinicians concede are still one or two evolutionary orders of magnitude away understanding the difference.

Mr Glencross co-authored homeopathy best-seller Therapeutics of Veterinary Homoeopathy and Repertory. For him, homeopathy is not a panacea to replace conventional medicine, but a complementary practice of proven efficacy which he has no hesitation in recommending for allergies, asthma and most common and chronic ailments. 'If someone is critically ill, get them to a hospital and a conventional doctor. Homeopathy isn't much use when the patient is dead. But what it can do is support and optimise the recovery. What we've found is that if you administer a homeopathic remedy at the same time as you are administering an aleopathic, or pharmaceutical, remedy, the need for the pharmaceutical will be reduced quite rapidly and can be gradually replaced by the homeopathic remedy.'

As for its use in the treatment of terminal diseases, such as cancer, Mr Glencross is refreshingly pragmatic. 'When people turn to homeopathy for terminal illness, it tends to be as a place of last resort when all else has failed - probably the best it can do is reduce the impact of the symptoms.

'But for your hay fever, swollen joints, common colds, fevers and so on it works and there is a lot of hard evidence behind it.'