I'd like to hear how this pans out.
Don't hold your breath. When this was originally raised on another forum, the driver's father confirmed that they had no intention of taking it further.
Sorry, I should have reported back.
As above, it was the driver's father who raised the issue. He reported back:
all sorted- she saw same officer by chance at the station who helped her with this
same documents produced and reviewed and car now ok to be released
reiterated that he didnt want to take car but was instructed to.
They are not taking it further. I got the impression that since the officer at the scene had been very helpful (she had, after all, driven into a ditch and presumably welcomed his help) they had no wish to involve him in a complaint. It seems he had no intention of seizing her car. It was only when his sergeant intervened that seizure reared its head.
As it happened, the unlawful seizure made no particular difference to her as she could not drive the vehicle away from the scene anyway. But it could have done and for a sergeant to be so clearly ignorant of the law (and somewhat devoid of common sense into the bargain) was very poor.