Let me give you an example of why LHR is such a mess using the overpriced HEX as an example. On arrival at LHR I expect to alight and follow travelators and escalators to emerge into T3. What I get is nasty concrete corridors with water dripping from the roofs, to emerge alongside a car park, to get onto a pavement to walk around some building works to finally emerge in front of T3, and exposed to whatever the elements happen to be throwing at us.

I can understand a central station, but link it directly to the terminals in an acceptable manner. This could have been delivered at the time of planning, and indeed Mott MacDonald proposed just this. Then the HEX tunnels collapsed and costs had to be cut. So we emerge into what was basically the rescue coffer dam.