And then there were 57. In one swoop Nationwide has reduced the dwindling ranks of Britain's building societies by two, swallowing up both the Derbyshire and the Cheshire, the No9 and No11 in the mutual hierarchy.

It is not a pretty ending for either surrendering society. Both have been chivvied into the arms of a stronger partner by an understandably anxious Financial Services Authority, which is more concerned there should not be another Rock-style depositor run than in the niceties of mutual merger etiquette.

Both had weakened their prospects and balance sheets by management mistakes. Derbyshire's blunderings in strategy, IT and treasury management suggest serious governance problems. Cheshire's difficulties were less egregious but it still managed to wipe out an entire year's profits with one duff loan decision.

It could have been worse. Both will retain their local identities and their branches, for now, anyway. And job cuts are likely to be less severe than in an equivalent listed bank merger.

It's hard luck on the members, who will get no windfall from the takeovers and aren't even allowed to vote on them. The three societies have seized upon a little-used clause in the Building Societies Act to bypass the tedious democratic business of consulting the owners before seizing their property (members can make representations to the FSA and much good may it do them).

Graham Beale, Nationwide's chief, insists that he is not running a charity for every wounded building society. But Nationwide is already an elephant surrounded by pygmies and these deals will exacerbate that polarity. The sector needs more than one big player if it is to be taken seriously.

The credit crunch could have been an opportunity for building societies, with their advantages of strong savings flows, customer loyalty and conservative ethos. Yet some of them appear to have strayed in precisely the same way as the banks.

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