Originally Posted by
Misco60
The OP doesn't provide his complete itinerary, so he could be travelling from a third country and only connecting at LHR. He also doesn't say what passport he holds: this is important, because a back-to-back isn't generally considered to be a transfer and BA might deny him boarding at LHR if he is not entitled to enter Bulgaria.
In any case, I'd consider an international back-to-back right now to be foolhardy.
I know that it's theoretically possible for somebody to be so desperate for BA TPs that they will start in a third country and connect via LHR to SOF only to turn around and go back to LHR. But it would be crazy in normal times, especially for an ex-SOF USA run...
Positioning flights should be direct from where you are to where you need to be, whether that's on FR, U2, W6 or any other airline. The added "safety" of doing a B2B on BA is completely lost if you are connecting instead of just starting your day in London...