Rarely will a report from the Competition Commission have brought so much joy to the hearts of so many. The thousands of passengers who were parted from their luggage during the disastrous opening of Heathrow's Terminal 5 in March got sweet revenge yesterday when the commission ordered BAA to be broken up.

As is often the case with revenge, however, the pleasure may quickly fade. As the commission makes clear, merely forcing BAA to sell Gatwick, Stansted and Glasgow or Edinburgh will not deliver better service from truly competitive airports. That will also require a great many other changes, including an overhaul of the regulatory regime.

The commission admits that the constraints on runway capacity in the South East will limit the benefits from competition in the short term. Indeed, as BAA points out, the commission also concedes that these constraints were the main reason for the poor standard of service at the airports.

And those constraints can hardly be blamed on BAA, let alone on Ferrovial, the Spanish group that bought the airports company for £10.3 billion in 2006.

So would Ferrovial be justified in feeling hard done by? Hardly. John Fingleton, head of the Office of Fair Trading, launched the investigation into BAA in the middle of Ferrovial's bid. And it was widely agreed that there was a strong case for BAA to be broken up.

The fact that Ferrovial went ahead, paying an extremely high price, perhaps reflected its confidence that if the worst came to the worst, it would have no trouble selling some of the airports in what was then a red-hot market for so-called infrastructure assets.

Since then, that market has turned distinctly chilly. Buyers such as Ferrovial liked to fund their deals with high levels of debt, supported by the steady earnings of the assets. Thanks to the credit crunch, that debt is hard to come by and much more expensive.

There will still be plenty of potential purchasers, not least from the infrastructure funds that raised billions from just such acquisitions, but if Ferrovial was forced to sell now, the prices on offer would wipe out a large chunk of the £2.6 billion that it put in.

Worse still, the financing of potential purchases will come under heavy scrutiny. The commission gave warning that BAA's heavy borrowings could constrain the ability of its airports to invest adequately. It would be a concern even for an individual airport to be owned by a company with a highly geared balance sheet, it said. That could further limit the prices that Ferrovial would get for disposals.

Not that there will be much sympathy in the security screening queues in Terminal 5.

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