Why 3 runways NW/SE at Heathrow
The central one was part of the original triangular 3 runway RAF style layout....what is now 27R/09L was laid that close to the A4 road (in the RAF layout) because the Perry Oaks Sewage works couldn't be moved quickly...these were expanded to the Star of David '6' runway civilian scheme again avoiding Perry Oaks, making the central runway NW/SE redundant eventually buried under the Central Area Terminal