The sanctions and the combined efforts of private citizens, we've never seen anything at this scale before," said Karin von Hippel, director-general of the Royal United Services Institute, a London think tank. "I do think it's incredibly impressive". "...I don't think Putin cares about diplomatic expulsions and other things that are happening, but once ordinary Russians start to hurt even more, he will worry about that spilling out into the streets and he can only control that for so long," she said. "The real existential question is what Putin does now that he has crossed the line and we can no longer accept him into the family of nations," she added. "He may feel he has no way out and do something even crazier."