Originally Posted by
HilFly
There is this in BA's conditions of carriage.
If you need to change any aspect of your transportation because of events beyond your control, you must contact us as soon as possible. We will use reasonable efforts to transport you to your next stopover or final destination, without re-calculating the fare.
However, it doesn't seem to be very easy to contact BA. I suppose that if you show that you have been on hold for two hours when you reach the check in desk that might count.