More than 4,000 people are taking part in the largest emergency training exercise ever held in Europe.

The operation is taking place at a disused power station near Dartford, and is simulating a building collapse near London Waterloo.

Emergency responders from the police, ambulance, local authorities and Transport for London are practicing a co-ordinated response.

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UK's biggest-ever disaster exercise

The exercise has seen a building collapse onto a mocked-up underground station.

More than 70 agencies are involved in the staged emergency, which will last four days.

Teams are also working in a specially constructed temporary mortuary.

VIDEO: The operation is the largest emergency training exercise ever held in Europe.

The scenario involves a tower block which is being renovated collapsing onto "Waterloo" tube station.

To create the most realistic environment possible, an entire tube station has been recreated and then "crushed" in a disused power station.

With more than 1,000 casualties, thousands of tonnes of rubble, seven tube carriages and hundreds of emergency service responders, Exercise Unified Response (EUR) has been more than a year in the planning.

Organisers say the exercise provides a realistic training environment for specialist Urban Search and Rescue teams from all over the country.

And the huge scale of the incident also gives a chance for specialist teams from the police and ambulance service plus local authorities to practise skills and functions that are rarely used.

Teams will also be working alongside firefighters from Italy, Hungary and Cyprus who will also be mobilised to the incident.

London Fire Commissioner Ron Dobson, said: "Exercises of this scale are important to ensure that we are always ready to respond no matter what happens.

"You can't get this sort of experience from a text book, we need to play it like it's real and ensure that should the worst happen, our response is effective and well coordinated.

"It's fitting that this exercise should be part of our 150th celebrations as it shows how we have developed as a Brigade.

"The modern fire service is no longer just about fires, we have a range of skills including carrying out complex rescues from height, detecting hazardous materials and rescuing people from water.

"However, Exercise Unified Response is not just about the rescues; an incident of this size affects everyone from thousands of stranded commuters who can't get home, to distraught relatives who can't reach loved ones.

"We are working with TfL, local councils and various voluntary organisations to simulate the wider and longer term impacts that any major disaster would have on the community.

"Although this scenario is not a terrorist attack, we will be practising procedures and systems that are common to any emergency that results in a large number of fatalities and injuries. For example, hundreds of people left the 7/7 London bombings without physical injury, but found themselves struggling psychologically in the years that followed.

"In this scenario police and local authorities will set up a Humanitarian Assistance Centre which offers information and support.

"The exercise will also be rigorously observed by independent evaluators and any lessons learned will be used to improve the way in which we respond to future emergency incidents."