The southbound loads to Heathrow on the last flight of the day were very light, about 30 people.
It's badly timed for overnight longhaul departures ex-LHR.
Northbound the load was very heavy indeed, just a few middle seats free in the last few rows. A surprising number had fast track entry (gold, silver card holders, full fare and connexions from business/first) at least 40 on the northbound. Which makes me hopeful for the future of the route. The number of Range Rovers and premiums metal in the shot stay was an eye-opener, but tallies with high numbers of "premium" customers. There were a surprising number of checked bags just from LHR as well, so O&D seems to be a part of the equation too. BA now offer free parking in the long stay carpark, with is walkable from the terminal. This is a big bonus.
Indeed, this route is no slot-sitter.