We have a more detailed idea today of one way some of the human deaths resulting from BSE may have been caused.

Following a thorough piece of research by health authorities in Leicestershire into five cases grouped in or near the village of Queniborough, a now unused, and soon to be illegal method of slaughter released the prion agent responsible for spreading the disease, contaminating meat in some butchers' shops.

Dr. Philip Monk, who led the study, and his team eliminated all the other possible factors in the five deaths and so isolated the common elements.

Broadly it came down to this: older cattle which had been fed meat and bonemeal and so picked up BSE were being slaughtered in a way that allowed their diseased brains to infect the rest of the meat.

In addition whereas bigger slaughterhouses hose down carcasses, the smaller ones only wiped the debris away, and so delivered the whole animal contaminated with BSE prions to local butchers.

Local butchers also sold the brain for traditional dishes.

Though Dr Monk's report provides a possible link in the Queniborough cases it doesn't explain why the same kind of slaughtering method hasn't led to many more cases and more clusters.

The Government's deputy chief medical officer, Dr Pat Troop, says that more research will be needed to shed light on these matters.

The committee of experts to which this task falls is SEAC, the independent Spongiform Encephalopathy Advisory Committee. One of its members Professor Roy Anderson from Imperial College told PM that today's report will help in the understanding of the incubation and spread of variant CJD.