I followed a BA 777 across Poland/Germany to London a few nights ago. He asked for descent when over Berlin to FL340. When asked by Berlin for the reason, the reply was, 'Fuel Temperature' so I guess new procedures are already in force. Any BA 777 drivers care to enlighten us?
If the failure had occurred to only one engine, then there could be myriad reasons why this happened.
The fact that both failed at the same time points to the only common factor and that is fuel.
I think the AAIB have it right and spending endless hours and bandwidth on even more speculation and second guessing seems a particularly pointless exercise.