(Stefan Rousseau/PA via AP) Britain's Foreign Secretary Boris Johnson leaves 10 Downing Street Monday March 12, 2018, after Prime Minister Theresa May summoned people to a meeting of the National Security Council (NSC) to be briefed on the latest intelligence on the nerve agent poisoning attack on Russian spy Sergei Skripal and his daughter Yulia, in London. Johnson said Friday it was "overwhelmingly likely" that Russian President Vladimir Putin was behind the poisoning of a Russian former spy, in the most direct British accusation against the Russian leader to date.