*You do not pass through immigration control when you are on Airside transit*
Gosh how uneducated are you? Can’t believe I’m wasting time on educating the basics.
There is no concept of airside transit from the UK to Ireland. That is never a thing since year 1923. I can’t believe I need to do an elementary history lesson.
In case you haven’t heard, Ireland, along with the Isle of Man, the Channel Islands and the UK, are all in the Common Travel Area and the UK treats all flights and ferries among these places as domestic routes.
Have you never ever taken a transit flight via the UK to Ireland? It sounds like you have never ever done or even heard of that.
You always always always go through immigration when you transit to Ireland. If you are a visa-required national, you will always always always be asked for a Standard Visitor Visa. This has been in place for the best of 30 years and have not been changed at all. It was only around 10 years ago where the UK and Ireland signed a visa deal to allow certain nationals to use an Irish visa to enter the UK.
And if you arrive in Heathrow, you must always always always queue for 2-3 hours to pass through immigration before you can proceed to see the boarding gate for any flights bound for Ireland. Our suggestion for most non-EU nationals that want to take a transit flight in the UK to Ireland is to allow at least 4 hours to pass through immigration, unless their passports are recognised by eGates. Only a handful number of countries such as Australia, Canada and the US are on that list, who wouldn’t be needing a visa anyway.
