Thought i would share some rather surprising info i came across last week.
We have been towing Shearwaters around the country with a L200 4x4 pick up for the last four years without problem, unfortunately the big end went on the way back from Devon recently, so we have just changed for an 03 Ford ranger 4x4. I prepared a info sheet to leave in the cab for the drivers.
I went onto the ford web site and found the following

from memory)
Kerb weight 1775kg ( truck empty, full tank and fluids no driver passengers)
Towing 750 kg unbraked ,2800kg braked - (100 kg more then the L200)
gross vehicle mass 5650kg ( weight of total maximum load on the truck: IE Kerb weight, driver, passenger, load in the truck and any towed weight.
But the towed weight cant be more than the weight of the towing vehicle.
EG: Our Shearwaters are approximately 2400kg on the trailer all up, so kerb weight of the Ford Ranger 1775kg driver 100kg? 1885kg which means we will have to add 515 kg into the back of the pick up to make it equal to the weight of the shearwater ( up to the GVM). The recommended towing weight is 85% of the towing vehicle. I have checked this applies to all vehicles !!. if we had of crashed our insurance would have been void.