Then what are they doing there in the first place?
Seriously??
OK, let's suppose a Heathrow departure leaves 27L going via DVR so it comes off and makes a turn to the left and heads towards DVR. It can climb quite happily except for the Gatwick departure off 26 that wants to go North or towards Clacton, or the City outbound that wants to go South or the Luton one that's going South In your scenario, one of these aircraft would have to fly miles out of its way to avoid the other to allow them to keep climbing and cross each other at 18000ft or so. And that's before you take into account anything out of Farnborough, Biggin, Northolt etc etc
I don't think you can make any sort of statement about the LTMA like yours without looking like you know nothing about what is going on there. I know you seem to have an axe to grind with the way ATC is done in this country, but until you understand it properly I'd suggest you stop grinding