All pins must be used, R clips must be fitted correctly, worn/lost clips must be replaced. Must be fitted to a non rusty chassis.Driving licence must have towing for over 3.5 ton! Tacho fitted on centre line or driver side if used for hire or reward (not over 25 years old vehicles). Tacho must be used correctly and driver within driving hours laws. Tacho if fitted must be calibrated and above board. CPC training may be required if working for company. Operators licence may be required. Permits for moving waste/going aboard.
Don't worry DVSA will issue fine any way as no Defender has towing mirrors pulling a caravan/incorrect numberplate/lights not working/break away cable wrapped round tow ball/outside lane of motorway/trailer board at incorrect height/length/trailer just plain defective. If in doubt seek medical/technical/legal advice.