The middle lane hoggers generally seem totally oblivious to everything going on around them.
I generally go round them rather than undertake just in case they unexpectedly move into the inside lane, but you'd think that people would take notice when a car comes up behind in the inside lane, moves across the whole carriageway to overtake in the outside lane and then moves back to the inside lane in front of you.
That would mean they're paying attention to the
traffic world around them. They are the people who drive into the side of other vehicles, don't give way, knock motorcyclists(who are not always innocent) off, are constantly distracted by their phones/passengers, slam on the brakes when surprised, write
it came from nowhere on their insurance claims, don't know where they're going etc etc.