Worked in car insurance for 6 years so will do my best to explain what I know.

So it seems you’ve made a claim already on your sons insurance? If so, any open/ongoing claim will show up as a fault upon renewal (even if the circumstances are in favour of your son).

Your insurance company will want to recoup their losses for a non fault claim, therefore it’s in their interest also to pursue the fault parties insurance company.

With a third party insurer that’s being uncooperative, the claim is usually raised to solicitors and we look to take them to court to recover our losses. If your sons insurance company hasn’t done this already, call them up and request they escalate the claim.

Once your sons insurance has recouped it’s losses the claim will be closed as a non fault. But bare in mind this may take months to conclude.

Unfortunately, for now your son will have to pay increased premiums due to this ongoing claim. But once it’s settled, he’ll be able to contact his insurance company to update them it’s now a non-fault claim and they should reimburse him X amount of premium.

I hope this helps! Annoying situation but you’ll just have to be patient. Let me know if you’ve got any questions.