Caught in intimidating waves, David Cameron and George Osborne are two talented politicians who are out of their depth. They soared to the top of politics far too early, half-formed as public figures. They had little experience in a shadow cabinet when they took over their party, and no ministerial pasts when they started to run a country in the midst of an economic crisis. If they had reached the top 10 years later they might have been commanding figures. Sadly for them, and more alarmingly for the country, they peaked when they still had much to learn.

They are by no means alone in this, but they are much the most exposed. In spite of the storms, both are still fairly effective performers. Most of the time they are calm and witty in the Commons and in interviews. But in terms of policy-making, and in the confused projection of their agenda, they struggle to stay afloat. For illumination, always follow the policy trail, not the public demeanour of the policy-makers.

The U turn on petrol duty is especially illuminating – both the manner in which it was announced and the decision itself. The panic-stricken political calculations are obvious. The Sun newspaper was running a campaign against the rise, incidentally showing that in the Leveson era this particular newspaper can still reduce politicians to fearful subservience.

Ed Balls had got in first, calling for the tax rise to be postponed and forming an alliance with the Sun in doing so. Osborne was contemplating a postponement of the rise, but Balls forced his hand. Balls made Michael Gove's early ministerial life something of a nightmare when he briefly shadowed him after the 2010 election. The right's current deification of Gove began only once Balls had moved on. Now Balls does the same to Osborne, who felt the need to announce the U-turn within hours of the Shadow Chancellor's interview on the subject rather than defend it for a little longer at Treasury Questions in the Commons on Tuesday.

There is a new mythology about U-turns, reinforced most recently by David Cameron during a weekend interview in which he argued that they are healthy, showing that the Government is listening. The indiscriminately sweeping defence is as misleading as the previous mythology that U-turns are always a sign of weakness. Sometimes a change of policy is sensible but a darkly comical series of changes point to deep uncertainty at the top about direction of policy, to an insecurity about being unpopular for more than 10 seconds, and to a lack of confidence in decisions taken.

The U-turn over petrol prices is especially significant because it marks more blatantly than other policy shifts a slight loosening of the so-called Plan A. Normally when Osborne announces a tax cut he at least affects to explain in some detail how it will be paid for. Now he loses at least half a billion pounds without any attempt to say which departments would make up the shortfall. Belatedly Osborne discovers that the economy is so fragile that rigid fiscal conservatism can cause even greater fragility. He tiptoes away from unyielding austerity, even if he tiptoed in a panic over the timing.

What is worrying is not the latest inevitable U-turn, but the original shallow thinking behind the Budget. When the proposals began to unravel, allies of Osborne insisted that the Chancellor had no alternative but to introduce contentious tax rises that his predecessors had deliberately avoided. He had a deficit to reduce and other tax cuts to pay for, including his own policy to reduce the top rate of tax for high earners, a crass miscalculation and one of the few measures from the Budget that still remain in place.

The Chancellor's allies were adamant that without these revenue-raising measures, Britain's tottering economy would move even closer to the edge. Now the apparently unavoidable tax-raising measures are dropped, suggesting that they were not an urgent necessity in the first place. The economy has not fallen over the cliff's edge without the tax on pasties.

We should not be surprised by the U-turns. They have been persistent since the youthful duo took over the leadership of the Conservative party in 2005. Like Cameron, Osborne follows the model of the historian AJP Taylor, who once declared that he had strong views weakly held. Osborne began his tenure as shadow chancellor by declaring his support for a flat tax. His support fell away quickly when even The Economist described the policy as too iniquitous and right-wing. Next Osborne moved to the centre ground, arguing that stability was his priority and not tax cuts. Soon after that, and fearing an early election, he announced a tax cut, the abolition of inheritance tax. With a flourish he soon went on to declare support for Labour's sending plans, and accused Labour of not spending enough in some areas. After which he leapt to the right of the Republican administration in the US by calling for real-term spending cuts in the UK when the financial crisis erupted in 2008 and governments were implementing a fiscal stimulus. This was in the relatively easy terrain of opposition. Cameron and Osborne exude great public confidence, so much so that they are seen in some quarters as cockily arrogant. I look at their erratic policy journey and wonder whether they know where they are going. I wonder more after Cameron's bizarre speech on welfare reform on Monday, in which tonally he made an irreversible leap rightwards from the compassionate Conservatism that had once been his defining tonal pitch.

Cameron/Osborne would have steered a more recognisably solid path, and acquired more consistently authentic public voices if they had toiled as ministers in departments or had fought long battles within their party. Sharp intelligence, instinct, and erratic attachment to re-heated Thatcherism are not enough in circumstances that demand unusually titanic leadership.