It is rare - perhaps unprecedented in recent years - to witness a government announcement about opening NHS beds, certainly in such numbers as health secretary Frank Dobson boasted last week. The government's pounds500m fund to tackle waiting lists would pay for an extra 2,000 beds in England, he claimed, and allow a further 1,100 that would otherwise have closed to be kept open.

Heady rhetoric about such an initiative reversing a 30-year trend ought to be regarded with scepticism. Tens of thousands of NHS beds have closed in that time; opening 2,000 does not reverse the trend, but it is an interesting little nick made against the grain. Will it be there for good, or will time soon erase all trace of it?

Beds have sometimes closed for perfectly sound reasons, of course. Medical advances have ensured that some conditions previously treated in hospital no longer need to be, and others can be treated more quickly. The average length of stay for acute specialties in 1974 was 10.5 days; 20 years later it had fallen to 5.4 days. And whereas 28 patients passed through every NHS bed in 1980, 54 did so by 1996.

Thus the NHS clearly needs fewer beds than it once did. Whether it has gone too far or not far enough is a complex question. Certainly, no manager would pretend that every bed closure in, say, the past three years has been made on clinical grounds alone: the growing financial pressure on the service has been the main impetus behind many, maybe most, closures, a fact that is admitted openly in places and disguised on occasion in others. With almost equal certainty, trends indicate that the NHS is nearing the point where it will have cut lengths of stay to the limit.

So Mr Dobson's announcement is welcome as a recognition that the move towards an NHS with ever fewer beds is not necessarily inexorable. Given the political corner into which the government has painted itself with its election manifesto's 'early pledge' to cut waiting lists by 100,000 at a time when they were rising fast, Mr Dobson had little choice. But NHS history shows that when ministers' interest wanes - once a target has been achieved - the problem blooms again. Will Mr Dobson's extra beds stay open for good? And how many more can we expect?