WHO, WHAT, WHY?
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Russia could expel British diplomats
The British Government has expelled four Russian diplomats from the UK following Moscow's refusal to hand over a former KGB agent accused of murdering Alexander Litvinenko. But why expel diplomats?
Relations between the UK and Russia are decidedly chilly - and look set to get colder.
Experts in diplomacy say Britain's expulsion of four Russian intelligence officers shows it means business over the extradition of Andrei Lugovoi - the man accused of murdering Mr Litvinenko in London last year. He denies involvement and Russia maintains its constitution prevents such a move.
The expulsions are intended to send "a clear and proportionate signal" to Russian authorities about the seriousness with which Britain regards the matter, says Foreign Secretary David Miliband.
Such a move is rare but used as a peaceful warning shot when countries fail to find common ground on controversial subjects, or when they feel the diplomats' presence jeopardises national interests.
A peaceful but significant signal that a country means business over a certain issue
Last year, India and Pakistan were involved in tit-for-tat expulsions over bombings in Mumbai. This year Fiji expelled New Zealand's top diplomat, accusing him of interfering in the country's domestic affairs.
Britain's decision, although regarded as modest by Cold War standards, could prove to be the start of an escalating series of diplomatic confrontations, according to some experts.
So far the practical impact of the expulsions is limited to the inconvenience experienced by the four diplomats involved and difficulties for other Russian officials visiting the UK, says BBC diplomatic correspondent Jonathan Marcus.
But Wyn Grant, professor of politics at the University of Warwick, says the move is significant not in its practical limitations, but what it represents - a breakdown of normal diplomatic relations between the two countries.
"Four diplomats is a modest number but it is meant to send a significant signal," he says. "It means Britain is likely to get a response from the other side, such as the Russians expelling British diplomats, perhaps in greater numbers."
If relations deteriorate still further Britain has other options, he adds.
After further rounds of expulsions, it could consider recalling the British ambassador from Russia. This could be followed by the breaking off of all official diplomatic ties - something the two countries are still a long way from, he says.
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But relations could decline quickly, if the numbers of diplomats thrown out of either country results in embassies being unable to function, he adds.
The diplomatic row over the extradition of Mr Lugovoi is not the first time Britain has forced Russian diplomats to pack their bags.
Former Conservative foreign secretary Sir Malcolm Rifkind expelled four accused of being spies in 1996.
He says the current confrontation is far worse because, as well as a British citizen having been poisoned in London, there are implications for those "considerably higher up the Kremlin chain of command".