or doing neither, accepting that there is a limit on capacity in the south east and look at alternative options that do not include increasing capacity in the south east - question whether transiting passengers add much to the national economy and whether domestic flights could somehow be removed totally.
Given we need to trade out of debt and the companies involved are mainly in the South East and the London area, no. Transiting passengers allow multiple daily flights to be served and drive down prices due to decent economies of scale. BA could not serve as many destinations so often from LHR is it did not feed. Consider the reason VS is in trouble is that it lacks the transit flights you see as not important.
Removing domestic flights would simply cut off regional airports from the main UK hub. Exactly how does that help to connect the UK to the world? Or do you just throw your hands up and say what the Hell, let's just gift all that traffic, revenue, frequent flyer loyalty and business to Lufthansa, Air France, KLM and the rest.
Typically British, we don't appreciate how very lucky we are until we are on the point of losing it. Again.