simonm, the reason why what you did "worked" is because of LocalRank. We're now dealing with LocalRank, it really has nothing to do with the so-called "sandbox" (which some say is a time-related penalty).
Google got a patent a few years ago that deals with ranking and re-ranking web pages. If you're interested in reading it, go to the
US Patent & Trademark Office, Patent Full-Text and Image Database and search for patent number 6,526,440.