The simple truth is, you are all the identification you will ever need, as there is only one of you.
Unfortunately in Legal land the policy enforcers are mostly unaware that they are trying to force you to commence in commerce, or contract. My personal opinion is that if someone has taken an oath to protect my unalienable rights, under the LAW, and then proceeds to in force company policy upon me, without the clear facts (Evidence) that I have consented to be one of the United Kingdoms company chattel, then lets play real life monopoly. Prevention is better than cure, rather than trying to give them the benefit of your vast over standing of blacks law,statute, legalese, unalienable rights ect. on the spot, you may decide for ease of movement and possible time constraints, to simply comply with there request for so called ID/ identification.