Let us, through gritted teeth, try to state a case for what has been done. The British Library has been commonly assumed until now to house a copy of virtually every book published in Britain since its collection was begun in 1662.

To ensure that its stocks are complete, publishers are required to supply, at their own expense, a copy of every new title. But books have had their own population explosion. More than 100,000 more are having to be accommodated every year. Some are Antony Beevor on Stalingrad; some are Catherine Cookson and some are India Knight. Others may be on Gauge Theory and Symplectic Geometry and Topology, or 2000 years of Zinc and Brass, or Environmental Factors and Cultural Measures Affecting the Nitrate Contents in Spinach (all titles now available from good bookshops). Not such grabby titles perhaps, but somebody needs them or they would not be published.

Even the British Library's new palace near St Pancras station in London does not have infinite space, though. Something has to give. Which is why the library has been winnowing: disposing of the books which, in its judgment, the world is least likely to miss.

You can see, then, what drove them to do it. In every other sense, what they have done is indefensible. Worst of all is the stealthiness. Faced with a genuine problem, they might have shared it with the reading public, appealing for help, advice and offers of extra storage space. They did not. The practice only came to light by accident, when people came across books purged from the library.

We do not know precisely who did the purging and how they decided which books should be sacrificed. On the basis of reports so far, it seems the work was assigned to junior staff. Yet anyone who has ever disposed of books knows how risky the process is. What seems wholly dispensable on the first of the month may seem irreplaceable by the end of it. I cannot be alone in having got rid of books and come within weeks to need them quite painfully - or even in having, from time to time, gone back to a second-hand bookshop to buy what I had sold.

Ask anyone who has ever written biography. Victorian England was full of rambling memoirs by people of little serious consequence outside their own eyes, with titles like A Statesman Looks Back, or My Life and Times. And yet sometimes the odd page or two in such books can be gold dust. You may suddenly, ploughing through their fustian (and too often unindexed) reaches, come across some whole uncharted new aspect of a far more famous statesman or writer with whom they had dealings. A few years ago, while researching the life of a Victorian fraudster, I came across two books of the sort which a junior winnower at the British Library might well have decided were of little future use: one the ponderous, meandering memoirs of a veteran of the construction industry, the other an overheated account of an old man's life in journalism. Both had encountered my quarry and had things to say about him which I had never found anywhere else.

As those who run the British Library know as well as anyone, that's the nature of research: unexpected sources are sometimes just as enlightening as the ones on your list when you started.

So winnowing books from collections calls for an expertise, a level of judgment, a degree of intuition perhaps, which is given to few; and is certainly not among the qualifications of every junior recruit to the library service. And yet some 80,000 books have been pitched into oblivion, lost for ever. Asked for a comment on Thursday, a British Library spokesman offered no more than this: "The discarding of books is an ongoing process." Which is rather like issuing confirmation that yes, you're still beating your wife.

Yesterday's Sunday Telegraph got something a bit more specific out of the library's director general, David Bradbury, who said that the purge would not obliterate anything published in Britain, and that most of the books which had gone were reference books which had since been updated. Neither point removes the offence. There are many, many books in the British Library which were published abroad but are nevertheless essential to scholars here; there are many reference books which though now out of date are invaluable source material. The latest guide to railway services in autumn 2000 doesn't erase the need for a 1910 Bradshaw.

As for the chief executive, Lynne Brindley, she has yet to emerge from her fortress at St Pancras to face her critics. Unless she does so this week, she may very soon find herself fingered as the Rebekah Wade of scholarship.