I have no idea how this transpired, but I do know how easily small things can escalate:
The other day I'd just started the engine on a C172 at Lydd, pulled the handbrake and made sure it held. I continued with me checklist and prepping my charts for several minutes whilst intermittently looking outside - still held. Then I took my eyes off it as I was taking down the ATIS and when I looked up the aircraft was in an ever so slight forward creep. Same 1200 RPM, same everything - the handbrake just decided to not play ball all of a sudden. We hadn't traveled more than 2ft, but still. Luckily it doesn't take much time to scribble down an ATIS, or it could have been much further.
I could see how something as innocuous as this could escalate into the above accident, if in a tightly packed parking area or not caught in time.
Lesson? Never trust Cessna parking brakes (especially the 152's - terrible system). Never look down or chase that elusively rolling Maltesters chocolate ball unless you can do so by still having en eye outside.
