I suspect it may have been something a little more than a hiccup etc.
I was there taking photos yesterday (the runway was 9L, by the way).
Following the arrival of a BA 787 at 14:19, I commented to another spotter that the wait for the next aircraft seemed extremely long.
Eventually a BA A320 arrived around 14:25, followed by the Lufthansa, then the Ethiopian. The gap between the BA 787 and the following traffic was around 7 or 8 minutes.
This was not the only "glitch" yesterday. Around an hour earlier, there was another longish gap between an American B777 and a BA A320. During this gap, an RAF C17 suddenly appeared, flying south to north more or less overhead the M25 at something like 2 to 3 thousand feet, cutting perpendicular across the 9L approach. Eventually, it made a left hand circuit and landed at Northolt. It seems this was the repatriation flight for the military nurse being repatriated from Freetown.