Parked on a pretty steep hill last night and got out of my car to talk to a mate. Was there for about 10 minutes when my car just started rolling backwards

Rolled about 30m down the hill and hit a Ford KA at the bottom!
I am gutted, Doesn`t look like too much damage to mine tbh, needs a new year bumber but hopefully everything else is ok. Although it may have done a bit of damage in the boot too...It looks like the boot lock has been pushed back a bit and is now rubbing on the plastic trim just inside the boot. It hit the other car at a fair speed and smacked it back about 6ft so front bumber etc looked a bit of a mess (even more so than normal)

Handbrake was on full but clearly it doesn`t like hills

Anyway its a good job the KA was at the bottom as if it wasn`t, my AGP would have ended up bouncing down some steps and out into the rush hr traffic on the main road...So at least there was a little bit of luck on my side.
I am absolutely gutted about it.