I have just read your response to a reader concerning how to join a motorway. The reader wrote that drivers joining the motorway have no right of way but your reply says otherwise. You wrote: “The priority is common sense. The driver of a car joining from a slip road usually cannot see traffic on the carriageway as clearly as drivers on the carriageway can see him. Any crashes that occur are often the result of stupidity or bloody mindedness by drivers on the carriageway who refuse to give way to the vehicles joining.”

Whilst it is true that some drivers already on the motorway don't move over where they can and it is safe to do so, fundamentally your questioner is correct. Rule 259 of the Highway Code states:

"Joining the motorway. When you join the motorway you will normally approach it from a road on the left (a slip road) or from an adjoining motorway. You should * give priority to traffic already on the motorway * check the traffic on the motorway and match your speed to fit safely into the traffic flow in the left-hand lane * not cross solid white lines that separate lanes or use the hard shoulder * stay on the slip road if it continues as an extra lane on the motorway * remain in the left-hand lane long enough to adjust to the speed of traffic before considering overtaking."

So it is indeed the case that it is up the driver who is joining the motorway to give way if necessary. If drivers already on the motorway move over to allow joining drivers to join, then that is no more than courtesy. The law itself is clear: if you are joining, you MUST give way to traffic already on the main road.