I called BA and the initial response was that there was a flight time change. I politely pointed out the flight seemed to remain unchanged in all aspects e.g timing, aircraft.

The next response was that there must be no seats available (which is strange in itself given we had been confirmed on the flight in business). I also noted that the flight was showing a lot of availability (Expert Flyer) and that tickets could still be purchased.

They then went away to investigate and returned to tell me that it seemed to be an error and they didn’t know why it had occurred. Happily they moved us all back to business and reissued the tickets.