Seasoned French politicians are well aware that the best time for unpopular announcements is August, when virtually the whole country shuts down and goes on holiday. Claude Allègre, the embattled minister for national education and research, appears to be no exception. At least not to judge by the timing of last week's controversial announcement that France is to become a full partner in the construction and operation of a new 3-GeV synchrotron facility, Diamond, being planned in Britain (see page 604).

There is much to commend this decision, even though it has angered a broad swathe of researchers — enthusiastically backed by local political leaders — who had been hoping to see their own proposed synchrotron, Soleil, built on French soil. Allègre is right to argue that economies of scale alone make it sensible that large research facilities should increasingly be planned at a European level. They should not be seen as public-works projects to mop up local unemployment or to burnish the electoral prospects of local politicians.

But the critics, too, have their points. Collaborating with Britain will save on the short-term costs of building two separate machines; but longer-term savings are more questionable. And many French researchers face the substantial costs of travelling hundreds of miles to carry out experiments that others will be able to do on their doorstep. Allègre owes his critics a full and detailed description of the calculations behind his decision. This is unlikely to placate them; but it may show that the decision has more logic than many now accept.