However, if you do Ireland -> UK -> EU, you'll most likely only see passport control between UK & EU. Passport controls aren't technically necessary between th

However, if you do Ireland -> UK -> EU, you'll most likely only see passport control between UK & EU. Passport controls aren't technically necessary between the UK & Ireland, but few airports in Ireland are architected to treat ingress differently. (I suspect in at least one case, they've actually gone backwards, as the domestic channel was repurposed for the US "ingress before you fly" method.) If you do the same trip in reverse, you're less likely to see passport controls entering the UK, as most larger airports are architected around domestic & International travel - Irish flights are usually landed as domestic.