Not for the first time in recent history, Russia appears to have committed murder or attempted murder on British soil. The poisoning of a former KGB agent Alexander Litvinenko in London in 2006 shocked the world but nothing was done about it. Now another former Russian agent, Sergei Skripal, has
Editorial: Putin's rogue state crosses borders to kill
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Almost 40 people may have been at risk if the chemical was delivered by spray, but the principle Russia has breached is just as important. For agents of a state to cross the borders of another state and carry out an attack on anyone, is an outrage to civilised international conduct.
It is an outrage this country experienced over the Rainbow Warrior which was not an intentional killing. This most certainly was intentional and might yet succeed. If the Skripals do survive they are likely to be crippled.
It is in the interests of all nations, and of international order, that national borders are respected even by spy agencies. And by large, borders are respected in espionage. Double agents were able to find safe haven in their adopted country during the Cold War but Putin's Russia appears to observe no such conventions.
There is not much civilised states can do in response but trade, sporting and diplomatic sanctions do count. As a writer in the Washington Post noted two years ago, when a British inquiry found Litvinenko's murder was probably approved by Putin, "The story of the past few years has been his steady descent from a leader welcomed and even feted around the world, to one whose hand is shaken only reluctantly."
Theresa May was Home Secretary when that finding was made. She told Parliament then Russia would face a tough response. This time she is in a position to see that it does. All countries should support her.