No mention has yet been made of the fact that HGVs are not allowed into the right most lane, where there are 3 or more lanes. This is where the 50 mph middle lane hog becomes a real PITA as they sit there oblivious, listening to radio 4. HGV in lane 1 (NOT the "slow lane"; it's supposed to be the default lane unless overtaking) doing his restricted maximum of 56 mph (this despite the speed limit for an HGV being 60 mph on motorways) comes upon Archers fan doing 50 mph in middle lane with nothing in front of them. HGV moves into lane 2, hoping that the car will move into lane 1 to let the lorry past. Car nobber with zero knowledge of highway code assumes HGV will use right most lane to pass, so doesn't move.
I see this happening frequently. HGV returns to lane 1 and overtakes up the inside. This could be legal or not, depending on the definition of "slower moving traffic".
HC rule 268 is open to interpretation.