Just curious to know what the pax on those 10 flights were told.
Probably that they would be landing at Heathrow.
LHR was previously forecast to be open by 19.00BST as part of the phased opening starting at 07.00 in the north. Notice that the BA flights started to arrive in time for that 19.00 opening - BA124 being the first to show up crossing the Dutch coast at about 18.45.
By the time it was announced that the planned re-opening wasn't going to happen, all BA's were en-route.
Who can blame them for continuing hoping for things to change.