Britain expelled four Russian diplomats on Monday in protest at Moscow’s failure to extradite to London Andrei Lugovoi, an ex-KGB officer and the main suspect in the murder of Alexander Litvinenko, a former KGB agent.

David Miliband, Britain’s foreign secretary, announced the expulsions in order to send Russia “a clear and proportionate signal”. In a statement to the British parliament, Mr Miliband said he was reviewing co-operation with Russia on a range of issues, while also freezing talks on loosening up visa regulations between the two nations.