This must be as they have released airframes from the TLV and CAI routes (which will now be served by a new midhaul product).
I wonder if it is a SE Asia destination or a South American one as these are the 2 key ares for growth as BA has stated.
SE Asia: The next one has to be KL especially with Malaysian joining OW.
S America: The obvious one is SCL in some ways. However, the 747 can only just make it. LHR-SCL 7,229nm and the 747-400 range is 7,260nm. Also 747-400 is just too big. A 777-200 can do it with range 7,720nm. The other option is that this is a tag on from GIG or GRU. GRU is a super busy route so not much capacity anyway and I thought GIG was doing really well so again may not be ideal. The other choice is Lima for S America.
FD.