Dave. I just do not understand the suggestion that a single runway could move more traffic than two runways. Heathrow is effectively two airfields - one for departure and one for arrival. Are you suggesting that if just one runway was employed the movement rate would increase? There are lots of other factors to consider. I worked Heathrow Tower for 20 years but know little about Gatwick, for example, where a high rate is achieved on one runway. How much crossing traffic does Gatwick have, for example? Heathrow's southern runway is constantly being crossed by traffic.