Which makes doing 50mph in the right lane ok because it's legal?
I refer my learned friend to the Highway code:
Motorways - Lane discipline (264 to 266) - The Highway Code
5. Lane discipline (264 to 266)
264
You should always drive in the left-hand lane when the road ahead is clear. If you are overtaking a number of slower-moving vehicles, you should return to the left-hand lane as soon as you are safely past.
FBW