Promises that if Heathrow is expanded, more regional destinations will be served are meaningless - neither the airport nor the Government can tell airlines where they should or shouldn't operate. If they can make more profit flying to Lima than Liverpool, that's what they'll do.
The Airports Commission acknowledged this, suggesting that even with expansion the number of UK routes from LHR will remain static or even decline in future.
Is it illegal post Brexit to ring fence a % of slots for domestic routes?
i.e. JER, GCI, IOM, LPL, LBA and maybe even MME?
For the benefit of the third runway, HAL would likely not see that as a dealbreaker.
Not beyond the wit of man to work this out surely?