I'm with IAG here.
Why should they fork out X amount of billions in funding the extra runaway, terminal and other infrastructure at Heathrow if they do not get first dibs on new slots.

The competition argument is flawed. No new airline can challenge BA entrenched position and even a new terminal and runaway will not help.

The competition is BA vs Lufty vs KLM vs AF vs ME3 at their respective hubs.

As far as I am concerned, BA can be as powerful as they can get at Heathrow because if they become too greedy and do not provide service, I will shift to KLM or ME3, etc.

A strong UK needs a strong. Heathrow and in turn a strong BA to maintain equilibrium in world aviation.

Without the above, we will become a second rate country which has sold off the national infrastructure to foreign entities.....oh wait, that ship has already sailed!