In London, the Government's Chief Vet, Jim Scudamore, appealed to farmers to make regular examinations of their sheep as it now appears that they may have been largely responsible for carrying the disease around Britain from a market in Cumbria.

Scudamore said that sheep could be carrying a "transient" form of the virus which might affect them only mildly, making symptoms difficult to spot. They do, however, pass it onto cattle, which react more violently.

"It is absolutely essential that the first signs in sheep are spotted and reported to the authorities at the earliest possible moment," he emphasised.

Emergency number

MAFF have set up an emergency phone line for farmers seeking advice about the latest regulations. It is:

0845 05 04 141.