The requirement is clearly set out in the ga briefing page on the inverness airport web site:
If you intend to leave the airside areas of the airport you will need to identify yourself to our security team on return. To allow ease of access please make sure you bring your pilot's licence and a recognised form of photographic ID with you.
So nothing to do with whether you are anglo-saxon or not!
No mention of it on the AIP entry for Inverness though if you happen not to check the hial website, although I don't know if it gets mentioned when you phone for the mandatory ppr. Does seem a bit draconian that if you are already airside, security cant give you some kind of temporary pass to allow you to re-enter on your return.
It's very easy to fly into any HIAL airport any time you like, without worrying about the opening hours, it only costs something like 20 quid and and a photocopy of your insurance certificate once a year to cover all the airports, which seems pretty fair and reasonable to me...