Leading article: A closure that will test the commitment to NHS reform

The hospital is the modern cathedral, a place of sanctuary and succour and an object of intense interest to the surrounding community. Any government questioning the life of a local hospital does so at its peril, and for the Tories, who have a fraught history with the NHS, hospital closures potentially are an even more toxic issue. Which is why the news we report today of the threat to one of London's oldest and most prestigious hospitals, St Mary's in Paddington, is bound to test Coalition nerves to the limit. Founded in 1845, it was where Alexander Fleming discovered penicillin. The strength of the outcry can be imagined if plans to sell off the site for conversion into 3,000 luxury flats get a go-ahead.

The background to the crisis behind St Mary's is a microcosm of the dilemmas facing the NHS as a whole as the Health Secretary, Andrew Lansley, struggles to reconcile the need for financial retrenchment with the demand for modernisation. The debts of the Imperial College Healthcare Trust, which runs five hospitals in London, have spiralled, now total £100m, and, as St Mary's stands on a prime site, the trust could save millions by selling the land and focusing activities on Hammersmith Hospital, which occupies a far less sought-after site in west London, near Wormwood Scrubs prison.

There is no easy answer to the question mark hanging over this and other, less well known hospitals. As Richard Taylor discovered in 2001, when he won the seat for Kidderminster in the general election on the single issue of keeping open his local hospital, this is a cause that can mobilise communities. That result was a warning to every MP: never underestimate the passions that hospitals can arouse. No wonder that MPs of all parties have been assiduous since then in pledging to fight to keep their constituency hospitals, or that Mr Lansley announced a moratorium on hospital closures last year.

The threat to St Mary's is a reminder that the issue of closures hasn't gone away, and that strong pressures tend in the opposite direction, not all of which are financial. Medically, there is an argument for concentrating the provision of services in centres of excellence, which means that some hospitals must go in order for others to attain the highest standards. The argument is stronger still in London, which is better endowed with hospitals than other parts of the country.

The Tomlinson report recommended closure of four in London back in 1992. Only one, the Middlesex, has closed since, principally because shutting a hospital in the capital, under Parliament's nose, is even more politically risky than trying to close one in somewhere like Kidderminster. In practice, in the absence of hospital closures, practices are changing on the ground. Emergency services are increasingly geared towards taking people past their local A&E to the nearest centre of excellence, on the grounds that the sacrifice involved in subjecting patients to longer journeying times to hospitals is more compensated for by the provision of bettercare.

St Mary's august history and high profile may gain it a reprieve from closure, but this won't substantially change the contours of the debate over the future of hospitals in the rest of the country.