Well, according to the new issue of
Fortean Times (#267), at any rate.
There's a great big article to tie in with the 70th anniversary about how secret occult rituals saved us from invasion, taking in authors Ian Fleming and Dennis Wheatley, artist Austin Osman Spare and of course the great liar himself, Aleister Crowley.
Only skim-read it so far, but much of it seems to be down to deception and misdirection (like any good magic trick) and the power of visualisation and positive thinking rather than fell demonic entities batling it out over the channel.
Still, could be useful/interesting for those who want to add a couple of real life characters to their games, or want to know the "real" reason Rudolf Hess made his trip to Scotland.
If you can't find a copy of the mag, they usually publish the previous month's lead articles on the website (here:
http://www.forteantimes.com/ ) so it will turn up there eventually.