Britain has recently expelled four Russian diplomats in some kind of childish hissy fit because Russia (obeying its constitution) declined to extradite Lugovoi to stand trial in Britain for the murder of Litvinenko a few months back.
The Russian government offered to put Lugovoi on trial in Russia for the murder, an offer which the British government refused.
So in response they expel four diplomats. Utter hypocrisy, Russia has been putting in requests for the billionaire tycoon Boris Berezovsky to be extradited for years, the most recent being in April. This guy fled to Britain with billions of dollars and claimed asylum and now escapes justice under the protection of the British government.
So let's keep things in context, Britain has been refusing to extradite wanted criminals, ranging from fraudsters to terrorists to Russia for years. The British government has no right whatsoever to complain about Russia declining extradiction.