Good reply.
I guess its purely down to rwy capacity then?
If so, as I previously mentioned, why isn't technology being used to its maximum to provide a constant flow?
I.e:
"Speedbird xxx please arrive at Biggin at 1354"......(this information could be supplied 100's of miles out)
"American xxx arrive at Compton at 1355"
All very basically put I know, but you get my idea?
My employer put's posters up everywher about turning a bloody printer off for the night, yet overhead there could be numerous heavies circling for the commercial gain of Heathrow!!
Edited to include that the

is not guided towards your reply !!