Three point turn accident

[francis40s]

I turned into a side road and there was somebody ahead doing a three point turn. They reached the opposite, ie their car was at an angle on the opposite side of the road. They then paused for a long time, during which I proceeded, believing they were letting me through. However, as my car was level with theirs, they began reversing, hitting the front right side of my car despite me hitting the brakes and coming to a stop. Damage was done to my car, and minor cosmetic damage to the rear of theirs. Who is responsible for this accident? Or should it be 50:50?