porton down

The head of Porton Down, the government’s military research facility, appears to have contradicted claims by the foreign secretary over the poisoning of a former spy, Sergei Skripal. Boris Johnson seemingly confirmed that scientists had “no doubt” that the nerve agent used was made in Russia. But Porton Down now says it has “not identified the precise source”.

When a former Russian spy and his daughter were found slumped on a park bench in Salisbury, it wasn’t long before investigators started looking at the Kremlin with suspicion. But how strong is the UK’s evidence against Russia? And what do the experts think?