But the dispute took an unexpected turn in mid-December when Russia ordered the British Council, a state-funded organization promoting British culture and language abroad, to shut down its regional offices by January 1. The council's Moscow office is not affected by the move.
Russia's Foreign Ministry said it would suspend operations of the two remaining regional branches outside Moscow, in St. Petersburg and Yekaterinburg, claiming the organization had breached the 1963 Vienna Convention on consular activities by failing to properly register its offices.
"We have had a number of discussions with the Russian authorities over the past three years, in particular about the status of the British Council," James Kennedy, the head of the British Council in Russia, told RFE/RL's Russian Service. "But their latest claims, that we are operating illegally, are completely new. The British Council is operating in Russia under a 1994 intergovernmental agreement on cooperation in the field of culture, education, and science."
The move came as a shock to both the British authorities and the many Russians familiar with the council's activities, particularly its English language classes. The only other countries where the organization has been banned are the repressive states of Iran and Myanmar.
In Britain, Prime Minister Gordon Brown was swift to condemn Russia's decision as "totally unacceptable," and urged the council to continue its work.
Many, like Kennedy, say the British Council is unjustly taking the brunt of political tensions. "The British Council is not a political organization. However, of course our work is affected by the bilateral political relations between Britain and Russia. But we feel that at a time when these relations are under strain, our work in culture and education is even more important," he said.
Despite Russia's initial assurances that the decision to shut down the council's regional offices is purely administrative, Foreign Minister Sergei Lavrov made it clear on December 12 that Moscow's stance was directly linked to the Litvinenko dispute.
In July, Britain expelled four Russian diplomats in response to Russia's refusal to extradite Andrei Lugovoi, Britain's main suspect in the 2006 poisoning murder of the former security officer in London. Russia followed suit by expelling four British diplomats.
"The British government undertook some actions which inflicted systemic damage to our relations," Lavrov told Britain's BBC. "They were inevitably calling for retaliation."
The British Council's language programs in Russia have already been hit by tax-evasion claims, which it has consistently disputed.
The order to close down the council's branches brings bilateral relations to a new low. But as Lyudmila Alekseyeva, a veteran Russian human rights campaigner, pointed out, the main victims this time are ordinary Russians.
"There is a well-known trend for our rich, our political elite, to send their children to study abroad," she said. "And the leading destination here is Britain. The British Council was an opportunity for less affluent people to obtain a good education, and this without the Russian government spending a cent. Now this opportunity will disappear."
The case is viewed by many as part of a broader campaign to undermine and intimidate British institutions in Russia.
Activists of the pro-Kremlin youth group Nashi staged daily pickets outside the British Embassy in Moscow for several months last year to demand the expulsion of British Ambassador Tony Brenton, whom they accuse of financing Russian opposition movements -- a claim British officials have dismissed as "absurd."
The protesters were back outside the British Embassy on December 5, just days after the sweeping victory of President Vladimir Putin's party, Unified Russia, in parliamentary elections.
In August, the BBC's Russian Service suffered a major setback when Russian authorities shut down its FM frequency, severely undermining the broadcaster's access to its Moscow audience.
The BBC, which is entirely funded by the British government, has also reported a series of physical attacks on its Moscow correspondents in the run-up to the elections. Two of the three victims were hospitalized with head injuries and a broken nose and ribs.
(RFE/RL's Russian Service contributed to this report)