"an encrypted ID number which allows access to specific information"

ahuh. having specced (or seens specs on) various governement systems in the past, and with the knowledge of what data the NIN would act as a 'key' to, I'd still say that the data isn't under the person's control at any point, nor is the release of same.

ps. the police already have access to DLVA info and I hardly think they would accept a backward step of having less information than currently!