At Flaps 1, you burn approx 5% more fuel than clean wing. Flaps 5 burn approx 12% more fuel (GE engines, not the RR most of QF has, but numbers should be similar).
Flying without flaps (at the appropriate speed), gives you as much margin, if not more, than flying at landing speed with landing flaps..........
Sounds like your crew was exercising good airmanship
