He didn’t break the rules
Yes, he did, @Pinkyxx The rules stated very clearly that if you or a member of the family shows possible covid symptoms, you stay put.
they clearly allowed anyone to seek help if they needed it.
"Seek" is the operative term there. They did not allow people to go out to get help somewhere else. In particularly, they did not allow anyone to drive 260 miles when there were various closer alternatives - notably, the nieces coming to them.
He wasn’t in contact with anyone at any point, thus couldn’t have spread anything.
This is utter nonsense. He says he didn't have to refuel during the journey - that means he must have filled up just beforehand. Immediate contact with people at the garage, the potential for him to spread the virus via the petrol pump. Before he started, he had no means of knowing that he wouldn't have to stop given that he had a 4 year old and a vomiting partner in the car, so he knowingly risked the possibility of further contact in the service area. The child and his mother were in contact with various people when they went to hospital. He had to fill up again before he went jaunting off to Barnard Castle. And so on, and so on.
If it was all so reasonable, why do you imagine his wife lied about it so blatantly?