Originally Posted by
Background Noise
I think it is still in the legislation - as a UK addition to SERA:
UK GM1 TO SERA SECTION 3 (GENERAL RULES AND COLLISION AVOIDANCE) CHAPTER 2 (AVOIDANCE OF COLLISIONS)
Following Line Features
An aircraft which is flying within the United Kingdom with the surface in sight and following a road, railway, canal or coastline, or any other line of landmarks, should fly to the right of the line feature unless flying within controlled airspace in accordance with instructions given by the appropriate air traffic control unit.