//Regardless of the legal position, if you see a car trying to join the motorway and don't adjust your speed to avoid a collision then you're too appalling a driver to be allowed on the road.//
I still get the cold shivers about being on the A19, my late OH pulled into the middle lane to allow the traffic coming down the slip road to join only to have some idiot pull onto the carriageway but continue into the middle lane. But for his prompt action there would have been a very nasty prang, I can still remember the look of shock and surprise on the face of the other driver, she clearly hadn't bothered to check the middle lane.