A massive two-day reconstruction of an outbreak of foot-and-mouth disease is being carried out by the UK government.
Thousands of animals were slaughtered during the epidemic
Ministers, officials and vets are taking part in a simulation of two days in the 2001 outbreak when the disease had spread to five separate areas.
They are considering ways to stop the virus, including measures rejected by ministers in 2001, such as vaccination.
The exercise, named Hornbeam, aims to help avoid a repeat of the real epidemic when six million animals died.
During the outbreak in 2001, the countryside became a no-go area for visitors and a complete ban on transport of livestock was ordered, but these measures are not being put in place during the simulation.
The task of those taking part is to respond to a scenario in which the disease has spread to five separate areas in the course of a week.
That is the point at which a decision would be made on the use of emergency vaccination.
Vaccination was repeatedly rejected in 2001, but the government will have to consider it in the simulation.
Animal Health and Welfare Minister Ben Bradshaw said vaccination was a "crucial area" to be tested.
He said: "It is essential that the department's ability to fight a new outbreak of this disease is tested thoroughly and that plans are realistic and achievable.
"Vaccination can be an important part of the armoury and a great deal of work has been done by the department in turning it into a practical possibility."
The seven-month foot-and-mouth outbreak left Britain's tourism trade in tatters.
And ministers were criticised over the handling of the crisis in an independent inquiry.
The Lessons Learned Inquiry recommended that the Army be brought in sooner to control any future outbreak.
The Hornbeam exercise was developed by the State Veterinary Service for the Department for Environment, Food and Rural Affairs.