When Dawn Sturgess and Charlie Rowley were taken to hospital, the emergency services tried to piece together what had happened to them. We hear how they questioned whether it was a coincidence that they had treated two people for nerve agent poisoning four months earlier or whether the events could be connected. And we find out about Porton Down, the UK government’s secretive laboratory which identified the Novichok and speak to a former military officer who has been inside.

This episode was made by Marie Lennon, Andy Howard, Tom Ryan & Dan O’Brien.

Executive production by Mary Sanders and Naomi Wordley.