I think you have to reason that anybody who intentionally drives like this with this attitude is going to be a bit pig headed about it.
There are just people that no matter what speed the middle lane is doing, they will just sit there. Too bloody scared to change lanes. The attitude displayed...
For one, your speedometer might be out by a couple of mph, someone else's might be out by a couple of mph the other way, so you could have 5 mph difference of 2 drivers thinking they're driving at 70.
If the driver behind is obeying the Highway Code, he is in the inside lane doing a couple of...
I didn't say they were law!?
You should only be concerned with your own driving, not others. It is irrelevant whether it is possible for someone to pass you within the legal speed limit, if the left hand lane is clear, then you should be in it if safe to do so.