People wouldn't undertake others if people didn't cruise in the middle lane leaving a 3 lane motorway as a a single carriage way, if they drove correctly others could safely use the 2 other lanes.
I know it's not big or clever but undertaking these fools generally gives them a hint. It really rages me when the inside lane is empty, outside is rammed and 1 pleb is pootling down the middle lane at 60mph.