Yes, our posts crossed. I wondered if it was something like that, but the harassed BA staff didn't know, and no-one was telling the poor SLFs like me (and some were much more disrupted than I was). And, of course, when you combine the flight I would have taken today with tomorrow's, it's full, so I now have to go via Vancouver and lose a day in Seattle. I'm sure the connecting Alaska Dash 8 will really feel great after the BA744 flying bed!
It would have been nice if the BA Executive Club had emailed me or called before I set off for the airport, given that they have my details and must have known about the cancellation. It would have saved them hassle as well as me -- T4 was getting almost dangerously overcrowded. Nothing on the BAA Heathrow Web site to warn intending passengers, either.