Farmers have been urged to show “relentless vigilance” in checking for foot-and-mouth disease, as officials become increasingly optimistic that the outbreak has been contained.

Debby Reynolds, chief veterinary officer, called for the “highest possible levels of biosecurity”, but said there had been a tremendous response to the operation to prevent the spread of the disease. A temporary control zone placed around a farm in Surrey that had been at the centre of the latest alert has been lifted, after tests proved negative.