The Police in Wiltshire are now launching a murder inquiry after a woman exposed to nerve agent Novichok in Wiltshire died. Dawn Sturgess died on Monday and her companion Charlie Rowley who was also exposed to the nerve agent remains critically ill in hospital. Police are no further closer to figuring how the pair got exposed to the nerve agent. Prime Minister Theresa May said she was "appalled and shocked" by the death which comes after the poisoning of Sergei Skripal and his daughter Yulia in Salisbury. The BBC's Security correspondent Frank Gardner talks to Guyon Espiner.