By tradition doctors were supposed to promise that they would “first do no harm”, although the phrase does not appear in the Hippocratic oath. Last week David Cameron was forced to withdraw his “cast-iron” pledge to hold a referendum on the Lisbon treaty. The Tory leader might do well to swear another oath before he measures the curtains for No 10: first make no more promises you can’t keep.

In committee room 14 on Wednesday the MPs and peers who crowded in to hear Cameron and William Hague sell the new European strategy scarcely murmured dissent. It was the sign of a party hungry for power: nobody was prepared to rock the boat a few months before a general election the Conservatives are expected to win. Potential troublemakers such as the former rival for the Tory crown, David Davis, and true sceptic believers such as William Cash lie doggo — for the moment.

“A year ago there would have been an outcry,” one close to the leader sighs with palpable relief. “Ten years ago the party might even have split.” Little Englander press reaction was muted. Even the Daily Mail leader that blasted his volte-face had a silver lining: an explicit endorsement of Cameron’s claims on No 10 that will not have gone unnoticed by the Tory high command — or by the prime minister.

Yet it has been a sorry business. The consti-treaty has been rammed down the throats of the peoples of Europe despite “no” votes in France, Holland and, at first, Ireland, until it was blackmailed into getting the answer “right” the second time round.

Labour’s abandonment of its 2005 manifesto promise to hold a UK referendum was a disgrace. Cameron’s fault was more forgivable: in his own words, Britain can no more undo Lisbon, now that the Czech president, Vaclav Klaus, has added his final signature to the treaty, than it can “stop the sun shining”. But he should have made it clearer from the outset that his promise of a referendum could be fulfilled only if the Tories won a general election before the treaty was ratified. “Heir to Blair” should not mean heir to his less attractive habits of prevarication.

Those suspicious of Cameron’s flexibility of principle, Eurosceptic or otherwise, will gather evidence against him. An interview in Standpoint magazine, for instance, suggests that the Conservative pledge to repeal the Human Rights Act made at the party conference also looks a bit shaky. Dominic Grieve, the shadow justice secretary, has promised a British bill of rights. But when? “I would like to think we could do it in the course of a parliament,” he says. It could be 2015 before the changes took effect. The practicalities are complex, but the party’s right wing and the red-top press will become impatient long before that far-off date.

The Tory inheritance from Brown next year will be thrice accursed, perhaps the worst circumstances in which to come to power since Margaret Thatcher took office in 1979.

First, the sick economy has curtailed the scope of ambition. Second, dark clouds now loom over foreign policy with a failing war in Afghanistan and an uncertain outlook in Europe. Third, the reserves of popular goodwill Cameron can call upon are low. Distrust of the political class, already damaged by the culture of spin, the failure to find weapons of mass destruction in Iraq and the expenses scandal, means he has to play it straight.

If the Conservative leader achieves a workable majority from the voters, he can shape the domestic agenda, within limits, to fulfil his pledges. In opposition, Cameron and the shadow chancellor, George Osborne, have changed course with each fluctuation of the economy: remember their unlamented policy of matching Labour’s spending plans? Now is the time for complete consistency. Osborne will tackle the budget deficit as the centrepiece of a Tory government’s first-term ambitions, a herculean task in itself.

Building on Blairite reforms, Michael Gove can construct the legislative framework of a Tory free-schools revolution, but how quickly it will take effect is unknown. In opposition, Cameron has chosen to ring-fence health and overseas aid spending, and he has probably invested too much of his prestige in these feelgood policies to change course without damage.

As for his Manchester conference speech boast that the Conservatives will outdo Labour in helping the poor, let us wait and see. True, Osborne promised to shield the low-paid from the worst of his proposed public service freeze, while Gove aims to give poorer parents a pupil premium, but the new “Red Toryism” has a lot to prove.

In the game of foreign affairs, Cameron holds few trump cards. Britain has to strain all its diplomatic skills as it is to influence the American superpower — Brown appears to have given up the attempt over Afghanistan, as we wait for Barack Obama to decide his next step. Negotiations with 26 European partners can never be win-win.

As foreign-secretary-in-waiting, Hague has some laudably ambitious ideas about restoring the prestige of the Foreign Office and creating a national security council that will co-ordinate defence, overseas aid and counterterrorism strategies. He will call on his crisp organisational skills as a former McKinsey man to put an end to “sofa government” decision-making in matters of war and peace. His close working relationship with Cameron and Osborne will also herald a welcome improvement: relations between No 10 and a succession of foreign secretaries have been poor during Labour’s years.

Hague wants to avoid a confrontation with Europe in the first year of Tory power in order to allow Cameron and Osborne room for manoeuvre at home. He would like to advance a positive European agenda on climate change and energy security. But the Conservative commitment to wrest back opt-outs on employment and criminal justice will not give him an easy ride. After Lisbon, Cameron promised not to “let matters rest” on Europe, yet letting matters rest is precisely what he will want to do initially. The Tory right wing will charge Hague with treachery if he gives up the fight. These circles will take some squaring.

Pierre Lellouche, France’s Europe minister, condemns any such attempt to claw back lost powers to Britain as “autistic”. Lellouche’s colourful language notwithstanding, Hague is hopeful of a good reception in France and even Spain. But the German centre-right government of Angela Merkel really is a bit cross that the Tories have left their joint grouping in the European parliament to set up their own small anti- federalist faction. And why should other countries pull British chestnuts out of the fire at this late stage?

There is also the small matter of the European presidency. Tory high command is highly pleased that its initial lobbying against Blair’s candidacy has been successful — a dull Belgian candidate with the interesting name of Rompuy is the frontrunner — but until a stake has been driven through his heart at the crossroads, I wouldn’t quite rule out our Tony’s ability to rise from the dead to glory in Brussels at Cameron’s expense.

In his speech on Wednesday, Cameron promised that, if he failed to secure his opt-outs from Brussels, in the next Conservative manifesto but one “we would not rule out a referendum on a wider package of guarantees to protect our democratic decisionmaking, while remaining, of course, a member of the European Union”. As post-dated cheques go, this one looks really unsafe. In any case both federalists and hardline sceptics might present it as an in-out vote on Europe.

One Tory predecessor, Harold Macmillan, famously boasted, “You’ve never had it so good.” If he takes office Cameron will find he’s never had it so bad. He would be wise to keep his commitments to a minimum accordingly.

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