Yeah, did they use the CENTER fuel tank? Plus a little assist from the Jet Stream I expect...
I wonder if they had legal IFR reserves.
"The plane had 360,732 pounds of fuel before the engines were started in Hong Kong -- more than the combined weight of the plane, its passengers and their bags. When it landed in London it had 18,700 pounds of fuel remaining."
It also says:
"The plane actually flew farther than the 13,422 miles that went into the record book. That's because the distance record is measured by a straight line from the start to each of the three turn points and finally to the end point at Heathrow. But the plane did not fly in a straight line between those points. The pilots would sometimes change course slightly to find better winds, although each of the three turn points had to be overflown. A flight map that is part of the jet's in-flight entertainment system showed the total miles flown just before landing at 14,042 miles."