I read about it for the first time in the Book of Acts. I am very surprised that I haven't seen this position advanced more frequently--it seems like such an obvious possibility that a smart guy like Paul might have realized that he could do more damage to the group from within.
So he was so willing to subvert Christianity that he was willing to suffer for it for it? The whippings, the prison sentences, the privations. Because he was martyred, you know. Doesn't sound to me like someone that was willing to damage Christianity from within to me at all.