By Peter Wilson
BBC Midlands Today, at Exercise Horizon
"We felt we would have died while we waited for the emergency services" is one family's experience of the UK's biggest mock terror exercise.
Volunteers acted as casualties of a mock gas attack
Standing in a car park for two hours with 400 other angry and confused nerve gas "victims" has left many unnerved at the prospect of a real terror attack.
Fed up with waiting, some have rushed the front doors of the NEC to try to find emergency crews themselves.
Like others, the Groce family say they felt abandoned by emergency crews.
Just after 0930 BST on Sunday several "suicide terrorists" played out a scenario of spraying nerve gas into a crowded hall 19 at Europe's busiest exhibition centre, near Birmingham.
The emergency services arrived minutes later, but until they were sure what they were up against no crews were deployed.
The "victims", dressed in tracksuits and T-shirts, were evacuated and security guards told them emergency crews would be with them imminently but the first fire engine did not move in to start decontamination until 1120 BST.
"We would have died waiting," said Astley and Deloris Groce, from Birmingham, who were taking part in the day-long exercise along with their three children.
They saw a crowd of people who were searching for help spill out of the front of the NEC and through an external cordon.
People were angry at the lack of communication about what was happening, they added.
As one photographer commented, the coffee and cream cakes arrived before the emergency services.
Meanwhile, two army volunteers also found time to escape the exercise and grab a cup of coffee with expectant media crews mingling at what was called Exercise Horizon.
"We could have escaped into Birmingham but, because this is just a training exercise, we thought we would have a cup of coffee instead," they told reporters, leaving organisers with much to reflect on after the region's first full scale "disaster".