UK 'will respond robustly' if state responsibility emerges over Russian ex-spy

British Foreign Secretary Boris Johnson has vowed that Britain will respond "robustly" if evidence of state responsibility emerges after a Russian double agent was left fighting for his life following suspected exposure to an unknown substance.

Sergei Skripal, 66, was found unconscious in Salisbury, Wiltshire, along with his 33-year-old daughter Yulia shortly after 4pm on Sunday.