An abundance of caution
Dominic Cummings’s perfectly reasonable not at all crazy explanation for that little side trip to Barnard Castle is that his eyes were wonky from his bout with COVID-19 so before driving himself and wife and child back to London from Durham he would take a little test drive (with child) to find out if he could see well enough to drive. As one does.
Bearing in mind that he was staying at his parents’ large, traffic-free private estate, it makes perfect sense that he would take himself and his family on a 20-some miles each-way drive on public roads to check that he was …. erm…. safe to drive on public roads.
Yes, that sounds like the kind of thing responsible adults would work out. “Ok, if I can make it to Barnard Castle and back without crashing, I’m good to drive to London. Deal?”
I’m still trying to understand what would be going on with someone’s eyesight that they would notice there’s an issue, but think that driving a car is the thing to test how bad it is. Like, hey I can’t read the label on this tin of beans, but let’s just check whether or not I can spot a motorcyclist in my wing mirror at 70mph before we make any rash decisions.