Timeline Slide 1 4 March: Three people exposed to a nerve agent in Salisbury 200m KEY LOCATIONS 8 March: UK Delegation to the OPCW informed the Technical Secretariat that two people had been taken seriously ill 12 March: Prime Minister publicly identified the substance used as a Novichok nerve agent. Russian Ambassador asked to explain Skripal’s house 13 March: Midnight deadline expired. No explanation received 14 March: Prime Minister set out the UK’s response 14 March: Prime Minister wrote to the OPCW Zizzi restaurant Shopping centre 18 March: Russia announced retaliatory action 19 March: OPCW team arrived in the UK Bishop’s Mill pub 20 March: 23 undeclared Russian intelligence officers expelled from the UK