A few more things to note on domestic connections. It used to be the case that there were a few BA agents sat at the entrance to the immigration queues, and that is where conformance would happen. This has now changed and conformance happens after immigration, and is a combined bp check and biometrics capture using automatic gates. The obvious downside to this is that if there is a lengthy immigration queue you could arrive before conformance but end up failing - I don't know what BA does with you if that happens as you are in an awkward spot and the rebooking desks are actually behind you on the other side of the border.

On the plus side it does mean that you can easily go and look at the queue length and decide to leave the immigration queue to head to the arrivals e-passport gates instead. Previously this was possible but you would have to ask one of the BA agents to remove the ready to fly marker before trying to go through security.

When the 5 new e-passport gates are on I would expect INT-DOM/DUB connections to be much better and I would probably head that way more rather than going landside which I have often done. The immigration queue was usually the slowest part of the connection, but the e-passport gates should change that. I may even have a go when I arrive back at T5 later this morning since I am connecting on to a domestic flight.