It's funny how many people hover between PPE and History. I did, and eventually opted for History. Sorry to say it, but the HAT isn't easy. Furthermore, there's a fairly crucial difference. The PPE test is taken while you're at Oxford i.e. after you've been invited to interview. The HAT is taken in early November before you're invited to interview i.e. it's used as a factor in deciding whether or not you're interviewed. This means the HAT has, in my humble opinion, much more pressure attached to it. If you mess up the PPE test, but have two storming interviews you may well get an offer. If you mess up the HAT, your PS and submitted work alone may not be enough to avail you an interview. Food for thought...