The row over the murder of ex-Russian agent Alexander Litvinenko in London marks a new low in Russian-UK relations, drawing comparisons with the Cold War.
In the past 25 years there have been several other diplomatic disputes between London and Moscow.
April 2007: Russia's chief prosecutor urges the UK to extradite London-based Russian tycoon Boris Berezovsky, who has claimed to be working for the overthrow of Russian President Vladimir Putin. Previously an ally of former President Boris Yeltsin, the billionaire is also accused of large-scale fraud.
December 2006: The UK embassy in Moscow complains to the Russian foreign ministry about harassment of Britain's ambassador by the Nashi youth group, which has links to the Kremlin. Nashi accuses the ambassador, Anthony Brenton, of having shown support for a "fascist" opposition group.
January 2006: Russia's main security service, the FSB, accuses British diplomats of using a fake rock on a Moscow street in a spying operation. It describes the device as "absolutely new spy technology". Footage purporting to show the "spies" using the rock is shown on Russian TV.
March 1996: Moscow expels nine British diplomats, alleging they are part of a spy ring. Britain expels four Russian diplomats in response.
November 1992: Vasily Mitrokhin, a KGB officer and archivist, defects to the UK after the USSR's collapse, smuggling out the contents of thousands of KGB files. His notes, collected over 30 years, are known as "The Mitrokhin Archive".
September 1985: USSR expels 25 British nationals in a tit-for-tat spy row, two days after the UK government orders the expulsion of 25 alleged Soviet spies.
July 1985: Oleg Gordievsky is smuggled to Finland by British agents and becomes the highest-ranking KGB officer to defect to Britain. He had spied for the UK while serving at the Soviet embassy in London and other diplomatic posts in Europe.