Ignoring who's to blame, it looks like you were not involved in the collision and that the accident was between the old woman and the woman that ran into her. So the fault is with either of them. The woman that rammed the old woman from behind is responsible for what is in front of her and paying due care and attention to the road and what is happening. With respect to them refusing to give you their details, if either of them hit the vehicle you were responsible for, then they have in fact broken the law, it in fact against the law to leave the scene of an accident and to fail to report it or give the other party your details irrespective of whose at fault or whether anyone is hurt or not. An individual can refuse to admit liability but cannot refuse details. I know this as fact from when our Freelander was hit when unattended in a car park and was hit by a woman who drove away and parked elsewhere. Luckily it was witnessed and reported by a 3rd party to the police with the reg of the offending driver. The police pursued her and after discussing with her and me as she was being uncoperative said they would prosecute her under criminal law for failing to report an accident and also failing to supply insurance details at the scene, which she should have left on the car or her contact details. She caved in with this threat.
