Is it true that a metro station was built under T1 in the 70s in anticipation of this? I know it sounds like a ridiculous rumour but I've heard it from more than one person who works in the airport? Supposedly directly beneath the disused spiral car parks between T1 and T2?
More than one tunnel under the airfield, Area 14 another example in T1
AFAIK.
Now the suitability for a Metro is questionable......