Sergei Skripal, a former Russian spy who is critically ill in the UK after exposure to an unknown substance, was one of four prisoners who were pardoned and released from custody in 2010 as part of a spy swap.

The US and Russia orchestrated the largest spy swap since the Cold War today in a tightly choreographed diplomatic dance.

Ten Russian agents who infiltrated suburban America and acted as spies were on a plane to Moscow today.