"Apparently it WASN'T a coincidence! He was well into that malarkey, although it's also the same diameter (or length, at least) as the Temple of Soloman (as mentioned in the Bible - '3 score cubits'), which, I think, is where it all tied up."
Stukeley, who was also well into that malarkey, reported that the top of Silbury was 60 cubits....