Why do they insist on passports at the Irish end and not the British end then?
Sometime in the late 90's they changed the law examine documents and refuse people are are not entitled to enter via CTA and while meant not to apply to British/Irish they are also covered because of the set up.
Thanks for the info. Seems like a strange rule to enforce but perhaps it is a product of the terminal design.
For T1 design yes, daa looked at CTA route when T2 was planned and connections would be far easier without clearing immigration but Goverment had no plans to change the law and with Brexit it will never change I suspect.