Welcome to Britain’s top secret laboratory where defences against chemical weapons, ballistics, explosives and cyber-security are researched.

The BBC was given access inside Porton Down to see what the highly secretive facility was like and, for the first time ever, entered a cleansed version of a level four laboratory. This level is where the Defence Science and Technology Laboratory team analyse some of the world’s deadliest viruses - Ebola and Marburg.

Frank Gardner, the BBC’s security correspondent, went to meet one of the scientists working there.

Filmed and produced by Samantha Everett and Imogen Anderson