Had just flown back from over 3280 feet with no problems. Decided to circle a water tower that was less than 800 feet from me. Thank goodness I always plan to fly higher than anything I'm flying around. I was flying FPV and did not notice that as I passed behind the water tower it blocked LOS to the P2V. As soon as the P2V past behind the water tower it lost the control signal (as well as FPV.) Before I had a chance to do anything , failsafe kicked in and the P2V headed home, which was of course was on the other side of the water tower. Video: http://youtu.be/Gc_BSTPyOxA Close call.