Don't think it's a new law. IIRC the limit was always 40, but rarely enforced. When I were no'but a lad, small van drivers.... sorry, drivers of small vans, not small drivers of vans .... used to get booked for doing more than 40.
Anyway, whatever speed they are doing, the combination of trucks, needless 50 limits / the national 60 limit, and speed (sorry, "safety") cameras, totally stuffs up any off-motorway journey because it's impossible to overtake the sodding things without risking a ticket. :thumbdown
And as for motorways and dual carriageways.... don't get me started! I'd just ban 'em from any lane but lane 1, then they couldn't just swerve out regardless of what's overtaking, or sit alongside another HGV for miles.
Apologies to any considerate HGV/PSV drivers out there, but your less considerate fellow "knights of the road" (yeah, right!) have tried to kill me too many times since I first took to the roads (about a million years ago).