Insurance companies aren't above the law Simon, for an insurance company not to pay out they have to prove the modification caused the accident, in other words it effected the road handling, another reason is if the mod has added value to the vehicle and made it more attractive to thieves, think about it, how many modifications have you actually made and declared ? bolted in pole hooks, roof rack, Speedliner, Protectakote , van wrap, ply lined, fitted shelving, tow bar, bolted in pole hose, split charger, upgraded battery, the list is endless.