Single-engine failure? Low down, low thrust, gusty cross-wind, down-draught/windshear.....could be tricky for the A/THR and PF to handle. Might explain steep bank angle and noise from one engine. I know, I know, this shouldn't cause an undershoot of such proportions, and this is mere speculation. Hope fully all will be revealed from the FDR and CVR.
Well done, BA crew and emergency services. Quick and positive response.