Other insurance denying liability, England

A van reversed from a parked bay straight into the side of me and I’ve been told today they’ve denied liability. Is this normal for insurance to deny liability or do they genuinely think they can somehow say it’s my fault? I have a witness who was present at the accident that looked over my baby as we had a 3 week old baby in the car with us.

The damage to my car was in the middle so it wasn’t like I hit him from the front as he was reversing onto the main road. He just reversed out straight into the side of me and clearly didn’t check, resulting in two need doors needing out on.

I’ve been told the third party insurance has denied liability and I have absolutely no reason at all to think why they believe this wasn’t their fault.