Theresa May’s assertion that it is highly likely the Russian state has committed an act of aggression by poisoning the double agent Sergei Skripal plunges Anglo-Russian relations into their worst state since the cruise missile crisis in the 1980s.
The prime minister knows that she will have to go further than her response as home secretary to the 2006 murder of Alexander Litvinenko – some assets frozen, an end to intelligence cooperation and the expulsion of a number of Russian diplomats.
Although the UK is giving Russia 24 hours to prove the murder came about due to rogue operators gaining control of military grade nerve agent, no one expects the Russian ambassador, Alexander Yakovenko, will even try to convince the foreign secretary, Boris Johnson, that the Russian state simply lost control of the poison.
Trust between the UK and Russia has been in short supply for years, and it is more likely Yakovenko will say Russia is the victim of media-induced spy fever.
It will leave May with no option but to confirm that the Russian state committed an unlawful use of force against the UK. That would place the onus on the Foreign Office not just to compile an effective unilateral response, but also to gather European and American support for a multilateral measures.
The context of Brexit, and Donald Trump’s ambivalence towards Putin, sets a diplomatic challenge for the Foreign Office. The UK has long been the anti-Russian outrider in Europe, and Johnson’s meeting with Russian foreign minister, Sergei Lavrov, in Moscow in December achieved little.
European Union countries come to the Russian issue with their own agendas and commercial interests. The EU foreign affairs chief, Federica Mogherini, has insisted the bloc was not suffering from sanctions fatigue over Ukraine, pointing to the imminent fourth anniversary of the annexation of Crimea. The EU competitiveness council on Monday renewed the existing sanctions regime.
But Angela Merkel, the reinstalled German chancellor, said she hoped the expected re-election of Vladimir Putin this weekend might provide a moment to restart the Minsk peace process. She favours further engagement.
The French president, Emmanuel Macron, on Monday fended off rare criticism of his Syrian policy from his predecessor François Hollande by defending his policy of engagement with Russia, arguing he did not think the years of complete absence of dialogue had led to any progress for France.
Equally the new Italian government, once it is formed, is likely to be influenced by the pro-Russian populist right.
Many experts say EU sanctions have probably reduced growth in Russia by just 1% last year. In a recent report, the Estonian intelligence agency claimed Putin “uses western sanctions to shield himself from criticism of a failed economic policy, and [this] helps to some degree to paper over the fundamental weaknesses in the economy”.
So the poisoning of a Russian double agent in a British cathedral city makes fascinating reading for European nations, but many Western politicians will be guided by bigger strategic choices including relations over Syria, Iran, Ukraine and commerce. Trump has also been reluctant to sanction Putin over alleged interference in the 2016 US election, with most of the running being made by Congress.
The likely UK unilateral package will start with the expulsion of some diplomats. Throwing out the ambassador would be a major step, and leave the UK bereft of a smart high-level conduit to Moscow. Retaliation, including the expulsion of the UK’s ambassador in Moscow, might follow.
The culture secretary, Matt Hancock, could in theory direct the broadcasting regulator Ofcom to investigate whether Russian media outlets such as RT are fit to hold a broadcasting licence. But state directed withdrawal of media licences might put the UK in the same frame as repressive regimes such as Turkey. Alternatively, public figures including shadow cabinet members, or even football managers such as Jose Mourinho, could be formally advised to pull out of the lucrative contracts they have signed to appear on RT.
It is also highly likely that sports officials, as opposed to players, will be directed not to attend the World Cup this summer.
More seriously, amendments to the sanctions and anti-money laundering bill will be introduced by ministers to allow stronger sanctions against human rights abusers, such as the persecutors of Sergei Magnitsky, the Russian tax accountant who died in jail in Russia after revealing details of massive state-sponsored fraud.
The Foreign Office says in practice it already has the full confiscatory powers it needs, but under pressure from Tory backbenchers, such as Richard Benyon and the Europe minister, Sir Alan Duncan, have said ministers will be minded to support a Magnitsky clause once the bill reaches report stage.
A more pertinent option would be to impose asset freezes on Russian oligarchs linked to the Kremlin especially if they are unable to explain the sources of London property wealth. But British law prides itself on due process, and arbitrary asset grabs in the manner of a Gulf crown prince might not look good.
Militarily, the British army already has a rotational presence in Estonia, but Russia would not welcome Nato placing more troops closer to Belarus.
Nato can also step up the strategic pressure on Moscow by speeding up Ukraine’s provisional admission into the alliance through agreeing a membership action plan. Similar encouragement to anti-Russian political forces can be offered in the Balkans, a key area of conflict with Russia. The UK is chairing a summit on the west Balkans this summer, and could use this as a vehicle to encourage parties fighting Moscow’s influence.
There are two other measures on the extremities of the spectrum of options available to Downing Street. The UK could designate Russia as a state sponsor of terror. In the US, designation results in a variety of unilateral sanctions, including a ban on arms-related exports and sales, prohibitions on economic assistance and visa bans.
The UK could also recommend Russian banks are cut off from Swift, the system behind international financial transactions. Some Russian banks linked to Iran have already been cut off from system, for instance. This might weaken Russia’s ability to trade internationally, but Russian banks have switched to a Russian payment system called SPFS, set up with larger non-G7 countries.
None of the options are simple, and in the end they will only confirm Putin in his apparent determination to define Russia by its opposition to the west, and especially Britain.