https://content.govdelivery.com/accounts/UKDVSA/bulletins/253c178 Click on the link full rule changes to the Highway Code. I wouldn’t rule out the possibility of this change being enforced by the gantry cameras.
Yup, a year ago or so When the smart motorways were getting completed, I was driving back from oop tnorth at about 2 am and 3 of the 4 lanes on the motorway had the red crosses on them so I moved out to the outside lane and after around 5 miles moved back to an inside lane as there were cars up my arse and undertaking, there was nothing going on in the inside lanes. After about another 5 miles the end signs came up and all went back to normal with no apparent hazards on the motorway, later I got a letter with a photo of my car stating there wouldn’t be s prosecution but asking if there was a reason I’d ignored the warning signs. So I guess it was an excercise to see what effect they had. So yes they will be enforced by cameras and you can bet your life there will be hefty fines.
Rule 259 is an intetesting one. I'm constantly amazed on how many drivers just barge onto the motorway, often forcing the traffic on the motorway to take evasive action. Makes my blood boil......