I'm not disputing the synergy of hubs, I'm disputing the importance of it in a part of the world which is so restricted in terms of runway (and airspace) capacity, serving one of the most important cities in the world.
Given that we aren't going to get another runway any time soon, the one we do get should be used to increase capacity into and out of London, not to increase the amount of people that spend two hours in the airport and only spend £4 on an overpriced sandwich in WHSmiths.
A new runway at Gatwick could double capacity overnight, an extra 40million per year. A third runway at Heathrow is going to increase capacity by 15-20million max, a third of which won't even enter the country. It's a no brainer.