I got stuck behind a white van man sat in the outside lane of a dual carriageway at 62mph this afternoon..... 
There was a big line of cars behind and he had plenty of opportunities to move over to let us all pass, but....... 
That's reminded me, any vehicle, large or small, is NOT alllowed in the outside lane(s) of a Motorway if it has a limiter fitted 
What
Even Aston Martins, BMWs etc, all of which are fitted with limiters

Think thats bollux 
Pop this in your pipe and smoke it...
The types of vehicles not permitted to use the right hand lane on a motorway (which has three or more lanes) are,
1. A goods vehicle having a maximum laden weight exceeding 7.5 tonnes,
2. A goods vehicle having a maximum laden weight exceeding 3.5 tonnes but not exceeding 7.5 tonnes, which is required to be fitted with a speed limiter
3. A goods vehicle which (among other things) cannot travel over 60mph
4. A passenger vehicle which is constructed or adapted to carry more than eight seated passengers in addition to the driver the maximum laden weight of which exceeds 7.5 tonnes; 5. A passenger vehicle which is constructed or adapted to carry more than eight seated passengers in addition to the driver the maximum laden weight of which does not exceed 7.5 tonnes, which is required to be fitted with a speed limiter.
6. A passenger vehicle which (among other things) cannot travel over 60mph
7. A vehicle drawing a trailer
8. A vehicle which is a motor tractor, a light locomotive or a heavy locomotive.
There are exceptions to this rule which are,
when it is necessary for the vehicle to be driven to enable it to pass another vehicle which is carrying or drawing a load of exceptional width. for a vehicle to change lane during a period when it would not be reasonably practicable for it to do so without involving danger of injury to any person or inconvenience to other traffic.
Any vehicle using the outside lane(s) must be capable of exceeding 60 mph. Simples.
People who are suggesting that lorries are travelling at 60+ mph are probably using their speedos to judge the speed of the lorries. If your speedo is saying 60mph, then you're almost certainly only doing 56/57mph at most. Almost all car speedos overread, hence there being no real excuse to being caught speeding. Truck (over 3.5t) speedos are generally calibrated along with the tachograph.
As I understand it, magnets etc are used to fool tachographs into thinking that the vehicle is stationary. This is for working time/driving time fraud purposes, not speed
