Whatever the moral, political, and historical reasons/rationalizations of Putin's seizure of Crimea, it's very clear that he did violate the provisions of Budapest Memorandum of 1994, by which Ukraine agreed to give up its nuclear weapons in return for guarantees of its territorial integrity by the US, UK and Russia. Since one of the supposed guarantors is the violator in question, that leaves the US and UK. The UK has been notably shy about applying its somewhat significant leverage. Why so?
A lot of Russian money flows through and to Britain. One version of the story is here.
If you’re looking for Russia’s weak point at the moment, you could do worse than start at a house on West Heath Road in leafy north London. It looks modest enough, but it would probably set you back $15 million.
It is the primary residence of Andrey Yakunin. His father, Russian Railways chief executive Vladimir Yakunin, is a former KGB agent and longtime pal of President Vladimir Putin. He was also a lead organizer of the Sochi Olympics and heads National Glory of Russia, an organization that aims to protect Russians from Western culture. (In a barely-readable book called Problems of Contemporary World Futurology, he predicted the collapse of the West in 10-20 years). His wife, Natalya, is in the same trade. She heads Sanctity of Motherhood, which propagates the “many-child family” through traditional Russian values and Orthodox Christianity. Their son Andrey is a fund manager, a graduate of the London Business School, and a specialist in “mid-market business hotels,” particularly ones that adjoin Russian train stations. His son, in turn, attends a posh English private school.
The Yakunin family is Putin’s Kremlin in microcosm, a hypocritical spookocracy that rejects everything about the West except its money, houses, and consumer goods. It also encapsulates the Kremlin’s weakness. If Putin’s Ukraine adventure causes Europe to freeze assets and inconvenience the Kremlin elite, then Putin will find himself losing support fast—from the constituency he needs the most.
The other side is that British real estate, schools, banks, and luxury goods markets of all kind like to bathe in Russian gold.
For the rest of Europe, the concern is even more substantive - It's heavily dependent on Russian natural gas.