A politician in the wrong is like a cornered stoat. The survival instinct brings on a surge of wild, furious aggression. The prime minister knew this week that a Commons select committee would revive the News of the World phone-hacking affair just as his culture secretary, Jeremy Hunt, had a prima facie case to answer over his handling of the News Corp bid for BSkyB. Every warning light should have flashed red alert.

There was a golden let-out, a perfect device for neutralising such delicacies: a reference to the cabinet's moral ombudsman, Sir Alex Allen. There was no need for a trial or witnesses or evidence in public. Allen was the old guard, a wink and a nudge in the club, a calming of nerves and a silencing of critics. Since time immemorial such methods have swept dirt under carpets or, if need be, placed revolvers in loos. Allen could have exonerated (or dispatched) Hunt, and David Cameron could have happily electioneered in Milton Keynes.

Instead the prime minister let loyalty and machismo cloud his judgment. On Monday in the Commons he as good as admitted it. Gone was the sad smile and shrug of the shoulders, the ever reasonable Cameron to whom every crisis is a minor affair of a pillow fight in the dorm. The nation saw a man at the end of his tether, purple with fury at his own mistake. "Weak and wrong," he bellowed at Ed Miliband, but it was Narcissus and his Echo.

Cameron has this month come of age as prime minister. He has found that being in government is not just about taking credit for everything and blame for nothing. It is about finessing error and gilding catastrophe. There is always some lobby taking offence, some election about to be lost, some document in the wrong hands or some minister in the wrong bed. The best Downing Street can hope for is the occasional distraction of a war or natural disaster.

The talk of Downing Street is that Cameron has modelled himself not on his party hero, Margaret Thatcher, but on Labour's Tony Blair. They share a likable public personality, a quick smile and mild self-deprecation. Both were perhaps overconfident in their command of parliament and TV studio. Both used the media as their mirrors and flew too close to Rupert Murdoch.

Blair is an ominous role model. Cameron has already acquired his addiction to foreign policy, to the anaesthetic of red carpet under foot and pointless meetings about nothing in particular. According to his office, he has gone abroad 42 times in under two years. To this has been added a dangerously short attention span for domestic affairs, a tendency to assume a headline-grabbing speech is sufficient to short-circuit the dull grind of policy formation from consultation through to implementation.

Both Blair and Cameron are prime ministers who had to learn about government on the job. It took Blair two years to complain of "the scars on my back" as Whitehall resisted his attempted reforms. He never knew how to make the civil service work for him, and even hired a "delivery unit" in Downing Street to show some gain from the gargantuan sums he showered on public services. It vanished into jargon and the Treasury.

Cameron likewise has had no executive experience. He started strong, with a message that budgetary austerity should be no impediment to radical reform. He committed himself to reducing the size and impact of the state. He wanted to decentralise power and responsibility, and build up the voluntary sector. The cabinet was united, the coalition robust. Compared with Thatcher in 1979, who faced similar economic troubles but with half her cabinet in open revolt, Cameron had everything going for him.

Within a year Cameron was copying not Thatcher but Blair. Civil servants, he said, were proving "the enemies of enterprise"; bureaucracy and over-regulation were intransigent. He could neither command the government machine nor give it the political direction that alone makes reform possible. When Thatcher's NHS upheaval got out of hand in 1988, she immersed herself in the detail and took personal charge of scaling it back. She would never have let cowboy builders rewrite her planning system. She would have read every line of George Osborne's recent budget, and seen the recklessness of cutting taxes on the rich while raising them on grannies, charities and churches.

Each crisis seems to take Cameron by surprise. Slashing the justice department by a third required him to support Kenneth Clarke's reductions in the prison population, instead of undermining them. Making political capital from errors in child welfare or passport control merely makes agencies risk-averse and adds to cost. Capitulating to navy lobbying on aircraft carriers wrecks defence ministry procurement discipline. Cameron's political brain does not seem to join the dots.

Real government is a dull grind, but it starts with political nous, of which Cameron's tightknit coterie seems bereft. There is a strength in loyalty to friends, but Notting Hill is not the best upland from which to survey the state of the nation. Cameron lacks a wise and cautious counsellor, a Whitelaw, a Heseltine, even a Prescott. Someone should have warned him about Hunt.

The civil service may have become a shadow of the institution that constructed the welfare state and later adjusted it to Thatcherism. But without it any prime minister is powerless. It must be led, and supported against the battalions of lobbyists that now beset it. Politics today may be fixated on the media's influence on government, but this pales against the influence of builders, farmers, defence contractors, drug manufacturers, energy companies or airlines. They have whole departments at their beck and call.

Cameron has established his austerity credentials, but has made little progress on reform, on localising and deregulating government and building his new sort of society. It's not that he lacks belief in such things, but that he left them to Osborne, who certainly lacks it. The truth is that Cameron in government has yet to learn the language of how.

When Thatcher got angry everyone knew why, because she was thwarted on her path to a known destination. Cameron's fury this week was to cover an error in the handling of an inappropriate ministerial relationship. When it passes he will be where he was before, with only the next crisis to confront. He seems a man stationary in the road, unsure of where he meant to be going.

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