lol, I had a similar jolt when boarding a LHR-DUB flight and the lady at the boarding pass check said "You don't need to show your passport for domestic flights." I didn't get into the conversation that it is BA that deems these flights domestic for the purposes of their security checks; that to use the term 'domestic' is incorrect. I realise it's in the CTA but it is a poor choice of wording. Also for most people boarding an aircraft, they show their passport as they board because for most flights you are required to show ID as you board (other airlines and stations require it, it is only those stations like LHR T5 that have the automated photo recognition at the gate that don't).