Is that a kink in the osr panel at roughly 2 o'clock on the wheelarch?

Suggest the pressure applied to the bumper might be more than meets the eye here, anyone's guess what's bent or cracked underneath.

Neighbour of ours got tapped everso gently up the back by another car, minor scuff mark much less than pictured here but when i dived underneath with a torch the steel underbumper was bent and kinked one side and the exhaust (brand new Puma) bent slightly down, third party was hoping to avoid insurance but sensibly our neighbour went via their insurer, just as well because the bodyshop tried to work a flanker by declaring no damage apart from bumper scuff, someone doing a crafty there, all sorted properly now.

As i pointed out on your other thread in Legal forum, you arn't just responsible for putting right the damage, the car being a renter the owner is entitled to loss of earnings, ie rentals, which could easly be several days and possibly a few weeks worth.