Skripal poisoning: Chemical weapons experts arrive in UK

Experts from the Organisation for the Prohibition of Chemical Weapons will arrive in the UK on Monday to test samples of the nerve agent used to poision a former Russian double agent and his daughter, in the city of Salisbury. British weapons experts say the nerve agent is of Russian origin, and the Kremlin has been asked to explain how it came to be used in England - if Russia itself did not authorise the attack. The Kremlin has denied involvement, and Russia's Ambassador to the EU has suggested that a nearby UK research laboratory - Britain's own military research facility at Porton Down - could have been the source of the chemical. However Vladimir Chizhov didn't offer any evidence. We talk to BBC political correspondent Rob Watson on the latest details.