Armed police and bomb disposal officers were called to the grounds of the District General Hospital on Wednesday for a mock exercise to test the emergency services and other agencies real time response to a major incident.
The training took place around the homes of nursing staff and doctors and a scenario was set to make it as realistic as possible.
Codenamed Operation Citizen, the exercise in Eastbourne centred around a dangerous culprit who had abandoned a car before making off in a stolen vehicle.
An area was cordoned off for the training and the Winter Garden was also used in the scenario as an evacuation centre.
The live exercise carried out by nearly 20 different agencies across Sussex drew to a close at 7pm. The major incident exercise involved nearly 400 people from the emergency services, local authorities, health trusts and other agencies and included 200 volunteers as victims and witnesses across Eastbourne, Brighton and Slaugham Manor.
Steve Voice, exercise director, said, “The scenarios we tested were exceptional and of a scale that tested our resources and provided very realistic settings at Brighton, Eastbourne and Slaugham Manor.
“We will be looking at the results of the exercise to see if there are areas of improvement that can be made to ensure that, should an event like this really happen, all emergency services work together effectively.
“We endeavoured to keep disruption to the public to a minimum and appreciated their support and understanding at those locations.
“I want to thank all those who took part, especially the volunteers who helped make it so realistic.”
Mr Voice said the exercise took place in public, albeit in designated areas, to make it as realistic as possible.
“It is extremely beneficial to the police and other agencies to test contingency plans, as directed by the Home Secretary, in a practical way and to continuously improve our service,” he said.