What does the article mean by "parallel to the M4" ?
Do they mean between the present 27R/09L and the M4 ? Surely not. This would place it on the present A4 and would necessitate destroying all the those swanky hotels on the Bath Road, not to mention conflict with the M4 spur etc. Perhaps there may be room somewhere on the alignment of the north perimeter road, but that would still necessitate a lot of destruction.
Could it be south of the present 27L/09R ? Hard to believe, given T4 and the cargo / VIP areas.
Just where could it be, even a shorter 6000 foot strip ? Maybe somewhere in the northwest corner of the airport towards Longford ??
And to think LHR was built originally with 6 runways (or 12 including reciprocals). ROFL