No actual specific legislation. The old point of refernce used to be the DFT guidance document https://www.gov.uk/gover...ehicle-operator-guidance However this got a gov.uk makeover yesterday https://www.gov.uk/gover...ehicle-operator-guidance

My view is that the headboard is to protect the occupants of the vehicle, more so if there is a window in the rear of the cab, so for example if the vehicle is loaded with steel beams they may go through the back window under braking then a headboard would prevent this from happening. If the trailer has a vehicle on the back of it or its a box trailer then their is not much of a risk of the load going through the rear window or the back of the cab. But your right, I have seen some vehicles with a load that could move and go into the cab with no headboards fitted. Note: the load of the vehicle is the drivers responsibility.

Thank you for your replies. I found a DfT Information sheet which states that it would be impractical for the legislation to be too specific in light of the different cargoes carried. As usual it comes down to our friend Risk Assessment. Thank you. Jomor