Sorry, I should have made it clearer: BA were looking for a solution that would have allowed the aircraft to be utilised in the timeframe available. That would have basically required BASSA to accept the ongoing situation and agree to waive the already-in-place disruption agreement, otherwise the flights would not have operated. They were being asked for crews to operate to minimum legal rest, which is less than that afforded by their disruption agreement, however an amount that the Flight Crew will operate to regularly whenever disruption occurs. And is fully legal. And is enough.
They did not do so. They required their disruption agreement to be honoured in full, despite the fact that that would have rendered the flights a no-go, leaving passengers stranded when the resources were potentially available to bring them to the UK.
So, and I should know this, the Devil truly lies in the detail!