There is nothing in the British constitution to curtail the time in office of one or other political party. Term limits do not work in parliamentary democracies. For all that, last week’s local elections were a reminder that the system does have checks and balances that militate against one-party rule. Nor are they any less potent for their informality.

The parties have offered all sorts of reasons for the drubbing Gordon Brown’s government received at the hands of local and London electors. The prime minister has shown unfamiliar contrition. David Cameron’s Conservatives have claimed tenancy of the political centre ground. The Liberal Democrats hung on with an entirely creditable result. It would be foolish to write off Nick Clegg.