A side question on the same topic. If I look up today's BA9 on BA.com it shows with the following message:
Flight delayed
We're sorry that this flight has been delayed.
If you're travelling on this flight and we haven't already contacted you, please check in and make sure you are at the airport in time for the original scheduled departure time.
Does this imply if you have been contacted, you do NOT have to be at the airport for the original departure time? You'd think there is always a chance the situation improves so you would want ALL passengers to be there. In which case why bother with the 'if we haven't already contacted you'?