In the Westminster bear pit, the weekly forum for MPs to question the prime minister, David Cameron excels at baiting Gordon Brown. Watching the prime minister on the ropes is good for Conservative morale, but the spectacle of Mr Brown at bay will not be enough to persuade the electorate to turn to the Tories. If Mr Cameron wants to be a convincing premier-in-waiting, he must seize the moment presented by Labour's evident exhaustion and the Liberal Democrats' search for a new leader. It is time for him to set out his stall.

Right now this does not involve de--tailed policy announcements. That would offer a distraction from the government's discomfort and hand Labour ideas or ammunition. In-stead it means communicating a clearer sense of what an incoming Conservative administration would stand for, as Margaret Thatcher did so successfully when leader of the opposition in the 1970s. There are two problems with Mr Cameron's programme as presented so far. It lacks an over-arching theme, and some individual elements are inadequate. It is, for ex-ample, frankly im-plausible that the cost of setting up a border police force and ending the early prisoner release scheme would be re-couped simply through the sa-vings from scrapping identity cards.