(as is the case in Madrid I believe)
MAD has four runways - two with 15/33 orientation and two with 18/36 orientation.
Regarding lengthening of LHR's northern runway westward: I guess the Queen would not mind ending up 2 miles closer to the end of the runway and with aircraft on approach over Windsor Castle 600 feet lower than today. The 1389 souls living in Rusper is definitely more important than the Queen.