(In February)
Was working in London and had a urgent requirement to be in ORD (Chicago O'Hare), cut a long story short, by the time I was in a taxi, there was 30 minutes to the Airport and around 45 minutes for the flight to take off. Had been in touch with BA and confirmed flight (with payment) by my office.
When I called BA, I was assured someone would meet me in departures and I should be OK for the 10:30AM flight, as long as I I have no significant delay in arriving.
They only said I could get was Economy as all the other seats were full, it is our policy to fly business, but due to the urgent requirement and the fact it sounds like they were going to literally hold the flight, I was grateful and understood fully.


Got to the Airport in the middle of boarding. Instead of going through the first wing, we went to some door and then through what looked like offices. I was HBO. (First question, is this a sneaky door?)
Got into the Terminal and on the Gate and there was still people boarding so all was well. Very nice of BA to do this and very grateful.
Got to gate. BP scanned, beep beep beep. Upgraded to First. This normally happens, but weird as there was no seats.. get into the plane and someone is sitting in the allocated seat. I would of probably considering the circumstances considered it a mistake and went to see If my Economy seat was occupied, however, as we are taken to our seats in first the CC asked to see our boarding passes.
We were both allocated the same seat. She then went to check what I assume is the master list (manifest) but for some reason could not put me to a seat.
After I explained my "day" she advised me to go back to my economy seat (poor me, but understandable) only for me to find out it was taken.
At this point, I think all cabins were counted, and it looked like they were close to doing a full cabin check.
I ended up in Business, (I have no issue). Around 10 minutes before take off and maybe 5 after the issue, the purser arrives with the iPad and a note asking me to move up to First as were was a mistake.

All a bit weird, and certainly no complaint from me was made, but my question would be are BA's systems no resilient enough for this? (e.g 2 people in 1 seat, people will no seats on board and two boarding passes the same even after the gate scan?) Any idea what happened? Was it because I was ticketed it maybe when boarding started? Just really want to know, 10/10 for BA that day.

Thanks