By Dominic Blake
BBC Radio Solent reporter, at Fort Widley, Portsmouth
Wrecked cars litter the entrance to a dark road tunnel while clouds of smoke and steam billow up from deep inside.
Swirling through the harsh beam of an arc light, they are pierced by silver streaks of heavy rain, before vanishing into the blackness of a pre-dawn sky.
Deep underground, a Hampshire Fire and Rescue Service team is at work.
They have abseiled into the void and spent most of the night fighting an underground fire.
It is cramped and dark, and their movement is painfully restricted by heavy breathing apparatus.
Above the rattle of portable generators the sound of grinding can be heard as the team cut mangled wreckage in the hope of finding survivors.
Soon, there will be the inevitable task of bringing out the dead.
It is just one of 35 frighteningly realistic scenarios being played out at Fort Widley during Exercise Orion, a multi-national urban search and rescue exercise.
Realism is the key. A five-storey block of flats has come down, killing many and trapping others in the rubble.
Emergency workers from across Europe joined in the exercise
Nearby, an old people's home has also given way and residents are missing. Cars are hanging from a motorway bridge. There is a constant threat from after-shocks. A fuel dump nearby could explode at any moment.
By the time Orion is finished, rescuers will have dealt with 600 simulated casualties and more than 2,000 fatalities.
Peter Crook, Hampshire Fire and Rescue Service's exercise director said: "It's a scene of total devastation.
"The first responders to arrive here were totally overwhelmed. Twenty fire engines would have struggled to cope. That's part of the challenge, and obviously deliberate."
The scale of the simulated disaster means that even national resources cannot cope.
Volunteers played the role of victims during the simulation
Europe's Civil Protection Mechanism, a network of emergency agencies across the continent, is activated.
Soon British rescuers are joined by seven urban search and rescue teams from as far as Germany, Spain and Sweden.
Peter Crook says the scale of the exercise is unprecedented.
He said: "It's a real challenge. We have a lot of live casualties, volunteers who will be rescued many times, but there are also a lot of simulated bodies.
"Dealing with the dead is a major part of this exercise. It sounds gory but that would be the reality. It is going to be hard, it's going to be tiring."
The teams are working around the clock on 12 hour shifts.
When it comes to the appalling weather, Mr Crook is stoic.
"If it's not raining - it's not training," he said.
Some of the world's most experienced responders are here as observers.
Bob Duemmel, from New York State's Urban Search and Task Force said rescuers around the world learned lessons from the 11 September attacks.
"Urban Search and Rescue is expensive, and prior to 9/11 it didn't get the attention it deserved. Since 9/11 there have been a lot of improvements in organisational accountability, planning and logistics."
It is a lesson which has not been lost on the European Union which has put almost a million Euros towards the cost of Exercise Orion.
Mr Duemmel said: "The more practice you do on your own, and the more often your practice together, it does nothing but produce positives in the long run."
"Confidence in yourself"
As Mr Duemmel speaks, the Hampshire fire team emerges from the collapsed road tunnel.
They are exhausted, but get on with cleaning the breathing apparatus they will need again in 12 hours time. I snatch a few words.
"It was difficult down there, arduous, but it's taught us a lot, and not just about search and rescue. It's also about confidence in yourself, and your training."
Another member of the team is hoarse from smoke and fatigue: "We were the second team into the tunnel. We had to squeeze into a tight space between a van and the tunnel floor. There's still a casualty down there. We're going to have to tunnel through a van to get to him.
"Every time we do training like this, our skills improve, but we get better at working in these condition. It's about getting used to it, so if this situation does ever arise we can get on with the job, and nail it."