not to mention fitting the shorthaul fleet for each in (although it would mostly be BA, ZB/TCX only really have 2 'waves' of departures).
A lot of traffic used to be bussed from the 130s and 140s, the based BA short haul fleet is pretty small with a good 1/3 based away over night and most of the over nighters would be gone before the bulk of the long haul BA B777s arrive. It's going to be 1988 again one more time
)