The man who made Novichok
The British government says a military-grade Novichok nerve agent of a type developed by Russia was used to poison former spy Sergei Skripal and his daughter Yulia.
Moscow denies any involvement. But a retired Russian scientist, Vladimir Uglev, says he manufactured a Novichok nerve agent which could have been the same one used on the Skripals.
He spoke to the BBC's Steve Rosenberg.