Suppose we assume 2 things:
1 - BAA / HAH is not going to see any significant monopoly inquiries in the UK for the next 10 years, having sold Gatwick, Stansted and Edinburgh
2 - Flybe is restored to good health in the next 2 years and remains the dominant carrier at Southampton.
As owner of both LHR and SOU, how much capacity does HAH have to make things difficult if Flybe launch new routes to major business centres (eg Madrid) in competition with Heathrow ?