40 Commando would be first on the ground in the event of a CBRN incident as the Lead Commando Group, but their brawn requires scientific brain behind it; at DSTL’s headquarters a team is on hand to provide the crucial information to tell them what dangers they face and how to deal with them.

“Because the threat is a technical, scientific one, the ability to reach out to organisations with specialist skills greater than ours is crucial,” said Lieutenant Colonel Paul Maynard, 40 Cdo’s Commanding Officer.

The three-week exercise included company-level attacks and various CBRN scenarios based on the latest threats for ultimate realism, such as a raid on a suspected chemical weapons lab.

It climaxes with a full-scale exercise involving government and industry scientists and more than 300 military personnel, including the RAF Regiment and the RM Band Service – casualty treatment was a key part of the Salisbury Plain exercise.

A chemical decontamination area was set up not merely to treat ‘polluted’ commandos, but also any wounded prisoners they may have brought in; once cleansed, casualties can be treated in field/regular hospitals.

Everything is a lot slower because of the chemical agents we come across with chemical casualties there’s the clean/dirty process to go through which is manpower intensive. First there is dry decontamination, a clean area to remove contaminate clothes, before moving to the wet area, where the naked casualty is hosed down.

“It’s quite hard work because everyone needs to get involved moving casualties – big lads with all their equipment on, they are quite heavy,” explained B/Sgt Caitlin O’Malley of RM Band Plymouth, helping to run the casualty clearance station.

"The chemical weapons suits and respirators don’t merely make stretcher bearing more difficult – they make everything more difficult. Walking. Talking. Breathing. Shooting."

"So it’s good that every year the Corps refreshes its skills with such an exercise", says Bravo’s Officer Commanding Maj Rob Garside.

“Working with DSTL means we have the most up-to-date information and a realistic exercise. This ensures we are well prepared for a CBRN operating environment.

“It is vital we can make rapid decisions and are able to protect and support specialists who come in to deal with any incident. On operations these specialists are on hand to advise and we must ensure we already have a strong understanding of their capabilities and what they require of us as a military force.”