A man who is critically ill after being exposed to an unknown substance in Wiltshire isa Russian national convicted of spying for Britain, the BBC understands.Sergei Skripal, 66, was granted refuge in the UK following a "spy swap" between the US and Russia in 2010.He and a woman, 33, were found unconscious on a bench at a shopping centrein Salisbury
The substance has not been identified.
Wiltshire Police are investigating