SALISBURY, ENGLAND – MARCH 06: Police officers stand outside the home of Sergei Skripal after a man and woman were found unconscious in Salisbury town centre two days previously, on March 6, 2018 in Salisbury, England. The man is believed to be Sergei Skripal, 66, who was granted refuge in the UK following a ‘spy swap’ between the US and Russia in 2010. The couple remain critically ill after being exposed to an ‘unknown substance’. (Photo by Dan Kitwood/Getty Images)