Its a Pan call.. " Plan to land at the nearest SUITABLE airport", bearing in mind there is no ILS on the failed side, crew workload will be higher than normal and I would not "assume" the battery will operate as it should. I certainly wouldn;t want to be in a holding stack or dithering around in this situation. As one comment stated, the situation at night would be even worse. General rule in BA was, anytime you're down to one of anything its a PAN. BOAC? care to comment