Britain's response to the poisoning of former Russian double agent Sergei Skripal on its soil, using a nerve agent developed by the Soviet Union, could hit members of the Russian elite hard if it closes the door on their London lifestyles.
Britain gave Russian President Vladimir Putin until today to provide an explanation for the attack, and is due to consider its official response tomorrow.
One possible counter-measure, suggested by British MP Tom Tugendhat, could involve denying Russia's so-called oligarchs access to the luxuries of London, where many have channelled their fortunes, traded their companies and relocated their family lives.
Most prominent among the residents of "Londongrad", as the British capital has been nicknamed for its popularity among the Russian elite, are Roman Abramovich and Alisher Usmanov, respectively owner and major shareholder of the English football clubs Chelsea and Arsenal.
But they are far from alone.
Around 10-15 per cent of the 96 Russians on the so-called "oligarch list" published by the US Treasury Department in January could have close ties to Britain, according to Vladimir Ashurkov, a businessman and critic of the Kremlin based in London.
"It's very possible that Britain will take measures that could affect these individuals," Ashurkov said.
"We know that London is a large haven for money that come from Russia ... Britain has the capacity to investigate this money and the activity of specific people," he added.
Among the best-known are a group of long-time business partners associated with the investment vehicle LetterOne, which sports three offices in London's wealthy Mayfair district alone.
The firm's founder, Mikhail Fridman, owns a mansion in London's Highgate, according to the company restoring the property.
One of the firm's investors, Petr Aven, has given journalists tours around his estate in Surrey, in the southeast of England.
Cutting Russians off from the British education system would also sting.
One of Fridman's children attends a prestigious British boarding school, photos on his social media account suggest.
Two sons of Russian entrepreneur and Tinkoff Bank owner Oleg Tinkov attend private school in Britain, according to their LinkedIn and Facebook profiles.
And two of Aven's children have described attending school in Britain before going on to study at Yale University in the United States.
Some wealthy Russians are in London specifically because they have fallen foul of the Kremlin.
After being fired as Moscow Mayor in 2010, Yuri Luzhkov moved his family to London, saying he feared for their safety.
Last December Yelena Baturina, Luzhkov's wife and Russia's wealthiest woman, was made a director of the charity the Mayor's Fund for London, according to Britain's business directory Companies House.
Their daughter Olga studied at University College London, her social media accounts show.
It is by no means certain that oligarchs bringing their money home would receive a warm welcome, said Christopher Weafer, senior partner at Macro-Advisory, a consultancy in Moscow.
"Oligarchs could find themselves in the middle, in the firing ground as it were," Weafer said.
- Reuters, AAP