The police chief in charge of reacting to a nuclear, biological or chemical attack has stressed the importance of the police being prepared for such an incident.
Mr Kelly says police have been preparing for attacks for years
David Kelly, the assistant chief constable of Kent Police told Police Review magazine if something happened, casualties would have to be expected.
He said he feared officers immediately on the scene would not be fully prepared for what they had to face.
Mr Kelly said that was one of the reasons it was so important to be prepared for an attack - and to reassure the public and officers that plans were in place.
Unsure what to expect
Mr Kelly told the Police Review: "My fear would be that we would get imprecise information and because of that imprecise information it is likely that our first responders would attend the scene not knowing what to expect.
"And, therefore, they would not have the protective equipment or training to deal with the incident."
There is not going to be the Armageddon effect that people are predicting
Assistant Chief Constable David Kelly
Mr Kelly said it was important to keep a sense of perspective if an attack did occur.
"If something happens, we have to expect we will incur casualties. But there is not going to be the Armageddon effect that people are predicting," he said.
"The first responsibility we have is to reassure people that, if we have one of these incidents, it is not the end of the world."
Planning for several years
He compared the aftermath of a chemical attack to other major incidents such as a bomb explosion or train or plane crash - events which cause immediate pandemonium but which the police soon bring under control.
Mr Kelly said the very fact it was possible an attack could take place meant the police needed to have a strategy.
"It would be naive of us to believe we could always prevent it," he said.
"They are going to get through, and when they do get through we have got to be able to put in this credible response."
He said the police had spent several years planning for an attack on the UK for several years.
"The police service has been considering chemical, biological, radiological or nuclear attacks since the Tokyo attacks took place in 1995."
But he told the Police Review his final message was to keep a sense of perspective - because the authorities are geared up and preparing to deal with an attack and the horror and fear it might generate.