Thanks for that Gonzo. Your first point more than explains what's involved here. The second one made me think a bit though; obviously the declared capacity at Heathrow is less with heavy aircraft inbound but given that almost all of these flights are already en route at the point that CTOTs start to be issued, should that not be factored into the equation? In other words, surely someone somewhere knows that of the X number of aircraft inbound, a known number will be heavies? Or am I overestimating the abilities of "the system"?
Also, you mention that much work is being done to improve flow management. Does that mean that a day will come when a CTOT is issued, we take off in accordance with it, no holding at the initial approach fix and a stand is available when we land? That's probably asking a bit much but how close to that ideal is feasible?