Originally Posted by HRGM
Correct. The UK and the Republic of Ireland form a common travel area where passports are not needed to travel between the two.
Actually, you do need a passport to travel between the UK & Ireland. At least non-EEA pax do.
Of course it's a requirement
in theory. I flew ATL-DUB-LCY over the summer and not once did any immigration official (American, Irish or British) ask to see my passport.
At DUB, I showed them my DUB-LCY boarding pass and was simply let into the country! And at LCY there was no immigration officer present.
Basically, I entered and exited Britain and Ireland undetected!