BA (and AA) don't really think they need an all business class airlines, they just don't want the competition of the Silverjets, et al. For example, AA started flying all business class to Stansted from one of the NY/NJ airports. They priced their product to be very competitive with Silverjet.
AA frequent flyers went with AA on the new route because it was cheaper by thousands than flying into LHR and they still got airmiles. AA has deep enough pockets to lose money on this route, until Silverjet folds. The day after Silverjet folds, they discontinued the flights into Stansted.
Which raises interesting questions vis a vis anti-trust...are they overcharging the customers to charge them £8,000 for NY-LHR business class? Or are they losing money to kill competition?