Originally Posted by
irishguy28
By evading the UK APD for a longhaul journey to Canada, and instead paying the UK APD for a shorthaul journey to Ireland, you are severely weakening your case. You cannot be travelling only to Ireland (for tax purposes, to avoid the large APD for a Canadian trip) *and* simultaneously be connecting onwards to Canada (for visa purposes) on the same journey.
This is true in theory but not in practice.
Immigration officers at the DUB transfer checkpoint will not care whether the passenger is on one or two tickets as long as they're satisfied they are genuinely going to clear off again. HMRC will not care about the passenger going off to Canada on a separate itinerary.
I second the recommendations above that checking baggage would be dangerous. I would also suggest using an EI prime flight (not BA) from LHR-DUB, and making every effort to obtain both boarding passes at the earliest possible moment.