Iceman, the ground environment at Heathrow isn't an artifical cap to movements. It is a physical reality. At the moment, the ground is a major limiting factor.
First thing in the morning when both runways are use for arrivals for the post curfew rush, T4 can fill up very quickly, thus leading to requests from the tower for increased spacing to the runway, or heaven help, T4 traffic landing on the north runway, and having to get down south. And when the departures start moving around 0630.
And reference good old RWY 23 for major crosswinds (only from the south mind you, and over the past 6 months, I have seen some hellish winds from the north! And remember, it doesn't have an ILS.), I'm sure my former Tower colleague will be far better informed to describe what it does to the ground environment, as it means the loss of parking stands as well as a taxi route.
The best thing for Heathrow - Nuke it and start again!!!
