The runway alternation procedure described by Groundloop started in 1972 and is fairly rigidly adhered to.
<<But isn't Feltham Cemetery almost two miles to the south from the centre line of runway 27L (corner of Sunbury Rd/Ashford Rd)? >>
I may have the wrong name for the cemetary. Where we go is 560m south of the 27L centreline and 100mm is about the most you need; I generally stick with a 24-105. The location is at approx 51 27.534N 000 25.057W.