David Cameron is determined to stay on and finish the job This prognosis was given wings by the Red Bull of Boris's star performance in 2012: he won a second mayoral election, became a global brand during the Olympics, and glowed with the Churchillian aura of a man awaiting the nation's call. For many disgruntled backbenchers, activists and (quite irrationally) the Right, he started to look like a blond-tufted panacea. For these impatient Tories, Cameron is the bed-blocker. When, oh when, will he leave? Today, they have their answer - though it is not the answer they want. Throughout my day with Cameron, I was struck by the frequency with which he talked about strategy, the long-term, the need for patience, the work of decades: what French historians call la longue durée. Whenever he referred to the Mid-Term Review, to be published tomorrow, he made clear that its scope stretched far beyond this parliament. Which prompted me to ask whether he would be stretching far beyond this parliament, too. Even in private, Cameron usually laughs off such questions, well aware that any definitive answer will send a depth-charge into his party and the political world generally. But, in our interview, he was unequivocal. He wants, if elected in 2015, to serve a full term - and explicitly not in the elastic sense used by Blair to mean "a bit more than two years." Thanks to the system of fixed-term parliaments introduced by the Coalition, Cameron is determined to stay in No 10 until 2020 at least. Which, by the way, would entail remaining Tory leader for 15 years, matching Churchill's and Thatcher's tenure of that role, trumping Peel and Disraeli. More to the point, he would become one of the longest-serving prime ministers of modern times, in the same league as Blair (10 years, 56 days) and the Iron Lady (11 years, 209 days), and ahead of Asquith, Churchill and Wilson. None of this, of course, will necessarily happen. Cameron has a mountain to climb if he is to win an outright majority in 2015 - the steepness of which is currently the matter of intense debate among pollsters. The importance of today's disclosure is what it tells us about him, his state of mind and his intentions. I do not think the scale of his personal ambition for power has changed. He is, after all, in the top job already, President of the G8 this year, at the apex of his profession. The certainty with which he discloses in our interview his determination to stick around is connected to reform and policy, rather than some crazed Nietzschean will to power. When he talks about "the roadmap in front of me" - economic recovery, education reform, the welfare revolution, transport, pensions, and much more - it is clear that the personal has become absolutely grafted on to the strategic. If Cameron has experienced an epiphany, it is that his mission is not simply to clear up Labour's mess but to prepare Britain for what he calls "the global race" - and that this will take the country, and him, many years to accomplish. A pragmatist by temperament, he has succumbed to the radicalism required by the times. I also form the powerful impression that he now sees himself as a practitioner of government first and of party politics second. It's not his job to appease "different segments of people" - such as Tories drawn to Ukip or outraged by gay marriage - but to "steer the ship in the right direction." He has returned from the Christmas break more convinced than ever that the national interest is to be found on the centre ground. There is no apology for his commitment to the NHS budget ring-fence, international development, greenery, and equal marriage: quite the opposite. To govern is to choose, and Cameron has clearly chosen. In moments of reflection, he concedes that the Tory message at the last election was confused, and that it must be straightforward next time: stick with compassionate conservatism and let us finish the job. Or, to be more precise, let me finish it. This supposedly laid-back Prime Minister today sends a few thousand volts mischievously coursing through the hungover political system. "Cameron 4 2020"? I can see the badges already.