I am not expert in aircraft fuel consumption, but a backroom statistician! Having looked at BA's website (fleet info), I worked out the following:
Concorde B747-400 B777-200
F/cap(ltr) 119500 216902 115991
F/cons(ltr) 25629/h 12788/h 4600/h
Pax 100 351 219
Does really imply (at least theoretically) thatConcorde can fly 4.7hrs; 747 17hrs; and 777 25.2hrs given the above stats and assuming consumption they give above is the average? (Capacity divided by consumption per hour).
Perhaps the news article tried to say the 777 is really light on fuel, and embelished a bit with its comparison :-)?