Pontius: I suggest you revisit the AAIB report on that flight. They had some very choice observations to make about the then -400 fuel balancing procedures that were in force in BA at that time. (they were at variance to the Boeing procedure) This is what led to the diversion landing short of LHR. The legally required total amount of fuel was indeed still onboard - it just was not in the correct places hence the crew`s concerns. IIRC BA were told to instigate appropriate training plus change their manuals.
(The crew were using the Jettison pumps to maintain balance - this works fine until you get to stand-pipe level...................)