Theresa May has given Moscow just over 24 hours to explain how a Russian, military-grade nerve agent could have been deployed in Salisbury against former spy Sergei Skripal and his daughter last week. Was it a direct attack by the Russian state on Britain? Or had Russia lost control of its deadly chemical weapons arsenal?
Should there be no credible response, the prime minister will conclude that the action was “an unlawful use of force by the Russian state against the United Kingdom” and will undertake “a range of measures” in response.
For such measures to be effective, they must be sufficiently punitive to deter Moscow from similar action in future and should be targeted to affect those who shape or benefit from Russian policy. Expelling Russian intelligence officers under diplomatic cover in Britain would, for example, be more effective than an eye-catching mass expulsion of Russian diplomats from the ambassador downwards.
Similarly, gestures such as boycotting the World Cup in Russia may not have much impact, not least because other countries are unlikely to follow suit. The most potent instrument Britain has at its disposal is, however, one which will be costly to deploy.
If the Salisbury attack is determined to be an unlawful use of force by Russia against an EU member state, should the EU not respond as it would to a terrorist attack?
London has long been the destination of choice for rich Russians, some with close ties to the Kremlin, for everything from financial services and expensive property to their children's education. Sanctions imposed by the European Union and the US after Russia's annexation of Crimea in 2014 have not prevented Russian oligarchs from laundering their wealth through London.
This financial laundromat is facilitated by an army of bankers, consultants, lawyers and accountants who profit handsomely from their wealthy Russian clients. Britain has already introduced Unexplained Wealth Orders but May’s government has until now declined to introduce legislation similar to the US Magnitsky Act, which imposes asset freezes and travel bans on named individuals implicated in human rights abuses and corruption.
Litvinenko murder
The attack on Skripal may be a test of Britain's strength after its feeble response to a 2015 investigation into Russia's state-sponsored murder of Alexander Litvinenko in 2006. But it is also a test of Britain's capacity to rally the support of allies in response to Russian aggression in the age of Donald Trump and Brexit.
A co-ordinated response with the European Union would enhance the impact of economic sanctions by making them more difficult to circumvent. And if the Salisbury attack is determined to be an unlawful use of force by Russia against an EU member state, should the EU not respond as it would to a terrorist attack?
Britain has made clear that it will not use its security capabilities as a bargaining chip with the EU and both sides have said they want a new security partnership after Brexit. Russia is a divisive issue in the EU, with some member states pressing for an easing of sanctions.
But a co-ordinated response to the Salisbury attack would be an encouraging down-payment on a post-Brexit security partnership that is in both parties’ interests.