Curious about this as well...

Reading all the old threads it seems like you can change a flight later in the itinerary once the first leg has been flown as long as it's 24 hrs before the flight in question. But the T&C still state that any changes must be made 24hrs before the first leg.

Can the BA rep clarify? (I read your 09 thread that said it wasn't official yet, but in practice you were able to change later flights after the first leg).