To be fair to the Crabs the delays into EGLL were not all their responsibilty.
Windshear and work on the new terminal had meant reduced arrival rate for most of the morning anyway. The ten minute flypast was just the last straw. Capacity was reduced for 1 hour by the way, so it sounds like the fly past was being used to buy some breathing space and get the air holding time down.
From some of the comments above seems it is better to wait on the ground than in the air anyway!