Russia is pondering how to respond to Britain's decision to expel four middle-ranking diplomats, over Russia's refusal to hand over the prime suspect in the murder of Alexander Litvinenko. Andrei Lugovoi is currently safely in Moscow, and the Russians say he can't leave, because Russia's constitution prohibits it.
The question here is how far the Russians will go in getting back at London. Chances are, in true Cold War style, we'll get some tit-for-tat expulsions of British diplomats from Moscow. But if President Putin decides to move against British business interests in Russia, particularly those oil companies with major interests in eastern Siberia, then things will start to warm up considerably. Then any sense of amusement at all this Cold War nostalgia will quickly turn to concern at what's becoming a big diplomatic crisis.