Bedfordshire Police, the Fire and Rescue service and the East of England Ambulance Service took part in a training exercise overnight to test their response to a terrorist style incident at The Mall in Luton and the airport.
The tri-force Joint Protective Services collaborated firearms unit were involved in the exercise that started at 9.30pm and went on into the early hours.
Around 200 role players took part in the event which involved a scenario testing the emergency services response to a multi-sited terrorist style incident including a marauding firearms attack.
It was carried out as part of the Bedfordshire Local Resilience Forum.
Assistant chief constable Mike Colbourne said: “It is incredibly important that staff from all emergency services regularly test their capabilities using a range of scenarios and we are very grateful to all our partners who made this exercise possible.
“Details were strictly embargoed until the night to ensure the situation was kept as authentic as possible for those taking part in the exercise.
“It was also held late at night in order to minimise disruption to the public.
“I would stress this exercise was not in response to any particular threat but clearly global events are a constant reminder of our need to be vigilant and prepared for every eventuality.”
The airport exercise was carried out in a closed area of the terminal, while police hand-delivered letters to businesses and residents living in immediate vicinity of The Mall last week, advising them of potential activity.
Officers patrolled the town centre during the exercise to reassure passers-by.