Here's why I'm sceptical about theories that involve a large number of people keeping a secret.
It's because the more people are involved, the more likely the secret will get out.
Good examples are, the Downing Street parties. It's now looking like Number 10 was one long frolic. Another good example was the MP expenses scandal.
Things like this, do get public, and I'd guess it's via someone who realised that it was all so wrong, and felt that they had to blow the whistle.