Re: Confession time
The Highway Code stated when I took my test that you shouldn't undertake unless there's a speed differential between lanes - otherwise - for example - if lane 1 was free flowing but for some reason lane 2 suddenly snarled up - by your reasoning lane 1 should also come to a halt - even if there was no reason to - because they'd be undertaking...
My copy of the highway code had a little set of images which had two cars travelling in the middle lane - the rear of the two cars passing on the inside (lane 1) of the front car in lane 2, before itself return to lane 2 - that was classed as undertaking.
Travelling at 70mph in lane 1 and driving past a car that's doing 60mph in lane 2, is not undertaking as far as the Highway code (when I took my test) was concerned.