The 'claim' that the soldiers are Russian doesn't come from UK/US politicians, it comes from Ukrainians.
I believe the the claims of Ukrainian politicians even less than I believe the claims of our own politicians.
The so-called Ukrainian government has never been elected and so cannot pretend to speak for the Ukrainian people. It is clear that many eastern Ukrainians want nothing to do with the Kiev regime because they are not represented.
We have only ourselves to blame for this mess because we did nothing to support the former democratically elected President of Ukraine, and stood by while he was toppled. It is inevitable now that Ukraine will split.