What is the reach of David Cameron’s ambition? Does he want to be the opposition leader who toppled Gordon Brown; or the next prime minister? The two need not be the same.

A month or so ago Mr Cameron would have struggled to answer the question honestly. The urgent priority then was to force the prime minister to abort an autumn election the Conservatives seemed certain to lose. Failing that, it seemed the best the Tory leader could hope for was to reduce or, with exceptional luck, wipe out Mr Brown’s majority.