The UK says that a Soviet-developed Novichok nerve agent [wikipedia.org] was used against Sergei Skripal, his daughter, and bystanders, and has given Russia "until midnight tonight" [npr.org] to explain how it came to be used:
British Foreign Secretary Boris Johnson said Tuesday that Russia has "until midnight tonight" to explain how a lethal Novichok nerve agent that was developed in Russia came to be used on U.K. soil. Johnson said Britain is preparing to take "commensurate but robust" action.
Reiterating British Prime Minister Theresa May's statement that it was "highly likely" Russia was to blame for the poisoning of former Russian spy Sergei Skripal and his daughter, Yulia, Johnson said, "the use of this nerve agent would represent the first use of nerve agents on the continent of Europe since the Second World War."
Meanwhile, police are probing the death of a Russian exile living in London [npr.org]:
Nikolai Glushkov, a Russian exile who was a close friend of a noted critic of President Vladimir Putin, has died from an "unexplained" cause in London, police say. The Metropolitan Police says that its counter-terrorism unit is handling the case "because of associations that the man is believed to have had."
Glushkov, 68, was a close friend of former Russian oligarch Boris Berezovsky, a prominent critic of the Kremlin who was found dead in 2013. At the time, an inquiry found he had hanged himself — but Glushkov publicly disputed the idea that his friend and former business ally would have killed himself.
As British media began reporting Glushkov's death, the police issued a statement saying, "An investigation is underway following the death of a man in his 60s in Kingston borough."