Ah, but mate it is an option. Heathrow can achieve a landing rate of 43+ arrivals per hour using one arrival runway with a mix of heavy and medium traffic, everything being vectored to the ILS (no visual sight and follows) in that stupid little chunk of airspace they have, and that is exactly the service every single approaching aircraft is given. Not sure of the exact movement rate, but Gatwick is exactly the same.
Not trying to stir !!!!!, just stating a fact.