There was a plan for a set of 3 runways north of the A4 dating from the 1940s which was publicly abandoned in the 1950s with newspaper headlines and local rejoicing, so somewhere in Whitehall you can be sure that the PLANS i.e, drawings survive
even if the current Government is opposed the the project (things change
)
What I would like to know from the professionals on this forum is whether air safety would be improved by having the 3rd parallel runway at Heathrow (increased separations?) similarly how much would safety be improved (and stress reduced) by giving Gatwick and Stansted 2nd parallel runways. Is there an ideal civil airport platform? e.g. 2 parallel runways with the terminal(s) laid down the centre?
Worth reading the Heathrow ATC book by Piket and Bish (and much input from one Brendan McCartney I believe) for the account of the interesting situations resulting from the use of 23L at LHR