The registered keeper is not always the legal owner. For example when they were looking at confiscating cars if you were caught exceeding 120mph my missus and I both signed papers to the effect of that although the cars were registered to us the cars were the legal property of each other. By doing this if I got busted for excess speed the courts couldn't take the car off me as I had signed and witnessed papers saying the vehicle was the legal property of my missus.