Having faced down David Cameron, Angela Merkel and Barack Obama in recent days over western opposition to Russia's military stranglehold on Crimea, Vladimir Putin now has the leader of the Liberal Democrats to contend with.
On Friday, Nick Clegg demanded Moscow enter into a "civilised dialogue" over the trouble in Ukraine, and even went as far as to say the Kremlin chief had a "KGB mentality rooted in the Cold War".
Attacking Putin directly, the deputy prime minister told The Guardian: "I think Putin's reaction is very revealing. It's as if he's been in a sort of deep freeze since the cold war and hasn't moved with the times. He gives every appearance of applying a KGB mentality rooted in the Cold War to new realities in 21st-century Europe.
"To regard closer ties between Ukraine and a non-military organisation like the European Union as the equivalent to American tanks on your lawn at the height of the Cold War suggests to me that we're dealing with a man who's applying yesterday's divisions and arguments to today's problems."
On Friday afternoon, it was reported that Russian forces had stormed a missile base in the Crimea peninsular while talks between Kiev and Moscow remain at a standstill, despite continued efforts by the EU and Washington.
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On Thursday, EU leaders threatened to impose asset freezes and travel bans unless there was swift action to end the stand-off and the White House announced visa restrictions and paved the way for further economic measures.
Prime Minister Cameron says Russia's "flagrant breach of international law" must be stood up to after predominantly Russian-speaking Crimea's parliament voted in favour of joining Russia, with a referendum to be staged on March 16.
He is expected to discuss the crisis when he meets with German Chancellor Angela Merkel on Sunday. Tensions rose further today when that proposed vote - dismissed as illegitimate by the new government in Kiev and its international supporters - was backed by both houses of the Russian parliament.
A team of Organisation for Security and Co-operation in Europe (OSCE) observers were once again barred from entering Crimea and there were reports 100 Russians had taken over a missile base in Sevastopol by force.
"It is now really for Russia to respond," Clegg told The Guardian. I very much hope they will respond by now agreeing to enter into that contact group and for a civilised discussion to take place between the Ukrainian and Russian governments."
Clegg accepted that Crimea - which was a part of Russia until as recently as 1954 when it was transferred by Soviet leader Nikita Khrushchev and is still home to its Black Sea Fleet - was in a different category to other parts of the country.
"Crimea already has a semi-autonomous status within Ukraine and clearly has a different history to other parts of Ukraine and has a very pronounced Russian imprint on it, not least because of the presence of the Russian Black Sea naval operation," the Deputy Prime Minister said.
"So it is already in a different category and I don't think anyone wants to deny that. No-one is somehow suggesting that Crimea should be treated exactly the same as other parts of Ukraine given that it hasn't been treated like that in the past by the Ukrainians themselves."
Putin was in the Russian resort of Sochi to open the Winter Paralympics - where the Ukrainian team pulled back from suggestions it could boycott the Games. But in what was seen as a symbolic protest, Ukraine was represented by just a single flagbearer at the opening ceremony.
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