"It just is" as so often seems to be the answer with these seemingly random fuel charges. This is the last BA bulletin I can find:

http://www.batraveltrade.com/trade/t...7/public/en_us

The amounts are out of date (see http://www.flyertalk.com/forum/briti...-298-37-a.html) but the principle is there - for >9 hour premium flights, it costs less to fly to Europe than the UK. Via the UK.

I suspect this has everything to do with market dynamics (what they can get away with charging vs. other airlines not flying to Europe indirectly via the UK) and absolutely nothing at all to do with fuel costs.