 after the hollow realpolitik that tolerated genocide in Rwanda and Srebrenica, the pendulum of British foreign policy swung to the ill-focused exuberance of the Blair-Brown era. From military overreach to implausible environmental targets, Britain has fallen short of many of her dizzying international ambitions. Now, amidst austerity at home, our foreign policy must be re-defined. Britain rightly sees herself as a global good citizen, but she must reconcile ambition with power, ends with means - shedding utopian idealism in favour of a more rugged internationalism, putting the national interest first, not last.  Take military intervention. Shrouded by the "dodgy dossier", which warped opaque intelligence, none of the stated war aims in Iraq spoke to the British national interest. Illusory dreams of bringing Western-style democracy to the Middle East were punctured by failures of planning and strategy, as catalogued before the Chilcot Inquiry. a similar chasm between ends and means haunts the brave efforts of troops in afghanistan. a surgical operation against al-Qaeda after 9/11 morphed into nationbuilding that one military chief estimates will require a military presence for up to 40 years. Likewise, humanitarian intervention, such as in Libya, requires international resolve, achievable goals and an exit strategy. Britain should scale down her current commitments and, in the short term, limit herself to wars of necessity.  Beyond immediate operations, our priorities must reflect our interests and capabilities. First, that requires robust affirmation of the right of self-defence to protect territory, allies, citizens and shipping - against judicial erosion by the International Criminal Court and the International Court of Justice.  Second, it means replacing ill-defined nation-building and regime change with support for fledgling democracies, and UN peace-keeping operations that combine international backing with local buy-in. Paul Collier, an Oxford economist, estimates that every ?1 spent on such UN deployments saves ?4 averting the costs of civil war. We have moral and selfish interests in containing the number of failing states fuelling terrorism, international crime and refugee flows. Third, as Lord ancram argues, a more independent foreign policy would allow Britain to become a major player in "peacemaking" - exerting influence by combining her diplomatic expertise with London's niche in mediating commercial disputes.  Beyond conflict resolution, our pledges to cut CO2 emissions should bind the major emitters and reflect viable plans to meet the targets. Given the failure to broker global agreements at Copenhagen and Cancun, Britain should pursue a deal with the 20 countries responsible for 80 per cent of CO2 emissions. UK targets should be shaped around domestic development of nuclear power - even after Fukushima, still the only affordable source of clean energy that can realistically meet the demands of businesses and consumers.  Taxpayers also want a further focusing of UK aid. Development strategy should be overhauled around a single objective: helping the poorest countries build infrastructure to strengthen economic growth, good governance and basic human rights. Middle-income countries with poorer regions should take greater responsibility for their own people - like India, in 2009/10 the largest recipient of UK aid, and now setting up its own aid agency. Too much aid leaks into military spending - Collier reckons 40 per cent of military spending by governments of the poorest "bottom billion" is funded by aid. British investment should reward governments that spend less on arms. aid should be harnessed more tightly to the national interest - it should, for example, tackle human trafficking, now 