During the Berlin airlift, aircraft were landing at Tegel and Templehof with 60 second intervals. The only way that could be achieved was if everyone flew at the same speed and at the assigned level they were given as they entered the three corridors. Once the maximum number of aircraft had landed, the airfield switched to departures at the same rate. The first aircraft to land was unloaded and ready to leave as the last aircraft landed.
It would be interesting to see if such a system would work for all the London airports, 2 hours of just arrivals, then 2 hours of just departures. It would certainly make flow control a lot simpler, bearing in mind that the technology available in the early 50s was somewaht less sophisticated than today's.
In case anyone is wondering, my tongue is lodged ever so slightly in my cheek, but only a little.