why should he do a undertake that is a bit grey area (most coppers will see it as a undertake and do you for dangerous driving), when the person hogging lane 2 should just move in and continue at his own pace?
I know passing on the left in traffic is fine but undertaking is not.
There is a very clear definition of undertaking, and a very clear definition of passing on the left, one is wrong and will get you nicked, the other one isnt, and wont.