Funny, Litvinenko didn't look muslim. It appears that the Russian price tag for practicing taquiya is rather steep. That or there was a 'workplace mishap' involved.
I'm not sure which possibility is more unsettling. Silencing separatists via radiation poisoning seems a bit much but the thought of fifth column Chechnyan's wandering around London with polonium in their pockets seems like a plot device that even Ian Fleming would have rejected as too outlandish.