Business people and staff from various organisations have been put through a simulation of a terrorist attack to assess how they would cope.
Project Argus, at the Crowne Plaza Hotel, Cambridge, on Wednesday, used sound recordings to simulate an attack.
Several explosions in quick succession on a busy summer's day in the city's Grafton Centre set the scene.
Those attending explored ways of coping with short and long term effects of an attack as well as preventing it.
Message for public
The event was held by Cambridgeshire Constabulary and the Association of Chief Police Officers, and Project Argus is an initiative run by the National Counter Terrorism Security Office.
Supt Simon Megicks, deputy divisional commander, said: "Project Argus was an extremely valuable exercise as it gave us the chance to bring businesses and organisations together to discuss how we, as a community, would respond to a terrorist attack.
"There was also an important prevention message. If you feel slightly suspicious about something, then listen to your instincts, as they are often not far wrong, and contact the police."
Project Argus events will also be held in other areas of Cambridgeshire.