The cause of the delay is quite a list:
It started with a delay of the crew getting into Heathrow as the crew had to transfer from T5 to T1
Once on the plane in Heathrow they had to go back to the stand due to a tech issue.
They got into the air and they were 2 hours 20 minutes late into Dublin. Now once at Dublin they turned the plane around quicker than Ryanair to get us all back to London.
But once on the plane there was a missing passenger with a bag in the hold so that was needed to be found.
Once they found the bag the captain came on to say that the flight path was now up and would need to apply for a new one. Which we got very quickly and we finally pushed off.
We then stayed on the tarmac for 3 hours due to a air pressure problem ( back to the stand, engineers onboard etc etc.)
We got into London 5 hours 1 minute late at 2am which meant that I had to get a taxi home at my own expense as there was no public transport.
It seems to me that most of it was a BA issue?