LGW doesn't make sense
- it's awkward for UK travellers unless they're in London or the SE
- It's not the main hub and wont work as a hub-let to LHR
Yes, and building a rwy at Gatwick while not building one at LHR fails to address the chronic lack of rwy capacity at the UK's only hub airport.
It's just a shame that all around LHR is so built up, but even if LHR had bought the land years ago they'd have wasted it building cargo terminals and whatnot and still want more rather than demolish their own 'essential buildings' (do they really need more terminal buildings or could they cope with what they have if they'd not filled it with overpriced retail outlets)
The land north of Heathrow between the A4 and the M4 has always been relatively under-urbanised, one could be forgiven for thinking that much of it was "safeguarded" for future rwy expansion (that never materialised).
Since the opening of LHR-5, terminal capacity is about right, and terminal development now is more about replacement, updating and consolidation than about expansion.