The British Airports Authority has only itself to blame for the ruling that it must sell off three of its seven airports. It is to be hoped that the the Competition Commission will now rule, after consultations across the industry, that one of those which must be sold is Heathrow. The BAA era has been one of poor service and failure to plan adequately for new capacity.

This has been seen at its worst in Heathrow. As a good number of the 68 million passengers who used it last year will confirm, the airport is little short of a national disgrace. The fiasco of Terminal 5's opening was only the most high-profile disaster. Heathrow had Europe's worst delays in the first quarter of this year, with 45 per cent of departures held for 15 minutes or more. BAA's monopoly was a key element in this failure. It has caused similar problems in Scotland. By contrast, Manchester airport, one of the few owned by someone else, has expanded smoothly.

BAA argues that selling off two of the London area airports – by which it means Gatwick and Stansted – will not, of itself, generate competition for Heathrow, because this is a "hub" airport, whose rivals are not other airports in the South-east of England, but Paris, Amsterdam and Frankfurt. This is true – up to a point. But to associate the success of these airports with their additional runway capacity, as is often done, is quite wrong. People prefer these airports because they have kept their focus on their main business – getting paying passengers to and from their planes and on their way, with their luggage, on time and in congenial surroundings. They have not skewed their business away from flying and towards high-profit shopping. They have not skimped on staffing for prime airport functions, such as security and baggage-handling.

Which brings us to another caveat. The regulators must resist any sale that amounts to a leveraged buy-out of the kind used by BAA's current owners, Ferrovial, who borrowed heavily to buy BAA and then piled the debt on to the airports. Particularly at a time of economic slowdown, this could mean cuts, job losses and a further deterioration in service. This is the last thing that any already substandard British airport needs.