(ec) Not apocryphal. Time Magazine (Stalin was "Man of the Year in its Jan 1 1939 issue)  is RS, and fairly contemporaneous to the event. The "undesirable classes" anecdote comes via novelist Gore Vidal, and is quite likely inaccurate. The version from Lady Astor otherwise conforms to the Time version. As does  Modern times: the world from the twenties to the nineties By Paul Johnson. As does  Russia's iron age By William Henry Chamberlin. Three reliable sources for the story. And apparently G. B. Shaw said that Astor was the only person in the world who could be bossy with Stalin, making the story quite believable. GBS' view  is quite horrifying indeed. "In Russia, on the other hand, extermination was carried out on a scientific and humane basis." Well worth having that in the article as well.