Passport to teach

I was asked to provide a copy of my passport by Virgin Active this week, to prove who I really am. I’ve been teaching there for over seven years! While I was scanning the recently renewed item I noticed an interesting comment at the back. Bordered by copper wire attached to a microchip were the words (in capitals) “the holder is entitled to re-admission to the United Kingdom”.
“Thank’s very much” I thought. Actually this is because I’m a British Subject and not a Citizen, born in India before the rules about British subject status changed. Pic, me with hair in 1975.