Agree with the stall, I think it was windshear. Looking at the metars for the day (I think it landed around 1300, correct me if I'm wrong):
EGLL 171150Z 20014KT 170V240 9999 FEW006 SCT010 09/08 Q0997
EGLL 171250Z 20013KT 9999 BKN008 10/08 Q0996 BECMG 24018G28KT SCT012 BKN020
EGLL 171350Z 22015KT 9999 FEW021 12/09 Q0995
Certainly a gusting, veering wind can do that.
Bearcat, don't agree with the "takes a hell of a lot to take a 777 to land short". Airspeed is airspeed, stall speed is stall speed. When one approaches the other you have problems, on a C172 or B777.