First, some uncomfortable facts for the Tories. The party’s share of the national vote has been on a plateau for a dozen years at about 32 to 33 per cent, with little shift since the general election in May.

As worrying is the decline in Tory support among previously core groups. Among the growing number of middle-class people, now well over half the electorate, the Tory share has fallen at each of the past four elections: from 54 per cent in 1992 to 37 per cent in May.

Similarly, among women, Tory support is down from 44 to 32 per cent. The real worry for the Tories is that they have so far lost the generational battle. In May, the party was third among those aged under 35, winning only just over a quarter of their votes, and narrowly behind the Liberal Democrats. Only among the retired, and near-retired, do the Tories still have an edge.

The Tories have to transform their public image. They have not been seen as a credibile alternative government, notably lagging well behind Labour on the central issue of competence in economic management.

A Populus poll for The Times in September showed that nearly three quarters of the public still said that the party seemed stuck in the past. More than two thirds thought that the Tories “just attacked the Government over whatever happens to be in the news, but never say anything positive”.

So the targets for Mr Cameron are clear, which he recognised in his speech. He challenged the comfortable habits and beliefs of many party stalwarts: on the “scandalous under-representation of women” among Tory MPs; on attitudes to modern Britain; on turning round inner cities; and on ending “the Punch and Judy politics of Westminster” (keep a close eye on Prime Minister’s Questions at noon today). These are the ambitious yardsticks by which he will now be judged.

Of course, we have been here before. William Hague, Iain Duncan Smith and Michael Howard each made fresh-start speeches about “reaching out” when they became leader, only for their efforts to falter in a repeated pattern of failure.

The closest parallel is with Tony Blair’s election as Labour leader in July 1994. There are similarities of mood, and language, especially the emphasis on changing the party. Of course, Labour was in a much stronger position then, already well ahead in the polls, than the Conservatives are now. One of the most fatuous gibes against Mr Cameron is that he is Blair Mark 2. That confuses means and ends. What the Cameron team is rightly studying, and in part copying, is the Blair electoral strategy, not his policies. Mr Cameron has to be equally clear-sighted, ruthless about jettisoning unpopular policies and focused on winning the centre ground. Mr Cameron won by a sufficiently large, two-to-one, margin to give himself considerable freedom of manoeuvre.

His power as party leader will never be stronger than this week.

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