More than 250 people were involved in the exercise In pictures: Emergency exercise

An exercise to see how Welsh emergency services would cope with a major incident like a terrorist attack has been held in north Wales.

An industrial estate in Wrexham was sealed off for the operation, codenamed Damaged Dragon. The aim was to test how well the "blue light" services - police, fire and ambulance - would be able to work with the Army, should disaster strike.

It began on Sunday morning with a controlled explosion at the Hoya lens factory.

North Wales Police were the first to go into the factory and they were able to assess that they were dealing with a chemical attack involving a dangerous nerve and blister agent.

The whole exercise, which involved around 250 people, was co-ordinated by the police, and took months of careful planning.

The scenario for the exercise was that extremists had been preparing a chemical to use as a weapon at the industrial park for use in London.

Briefing notes said the majority of the chemical had been prepared and was ready to be used. But, at the last minute, the terrorist responsible had a crisis of conscience and decided to destroy the lab - causing an explosion.

It was the first time an operation on this kind of scale had taken place in north Wales.

The mock exercise saw soldiers pretending to be injured

Chief Inspector Lyn Adams from North Wales Police said the emergency services found the exercise very helpful.

"Once you have a plan, you need to test that plan," he said. "It went very well indeed."

Army officers doubled up as realistic-looking casualties during the incident and were treated in decontamination units.

After being washed down they were taken to a community centre in Rhosddu near Wrexham, where members of the council's social services department were on hand to help them.

Wrexham was chosen as the location for the exercise because the local authority has been actively involved in civil defence planning.

However, police were keen to stress that the procedure was a practice and there is no evidence to suggest that the town could be involved in a similar incident in real life.

Wrexham Council chief executive Isobel Garner said the operation was an essential part of everyone's training in coping with such an emergency.

"We have no wish to alarm people by holding such an exercise, but we believe it would be irresponsible not to test our arrangements for dealing with a civil emergency," she said.