The coalition: Off the chart More than members of Britain's two main political parties, they pride themselves on being a nerdy bunch keen on theory and strategy. And they love coalition government - not least as it is the only way they can hold power. Characteristically, then, their story of the current one is both pointy-headed and optimistic. Ever since their deal with the Conservatives in 2010, Lib Dem advisers have predicted that the five-year partnership will divide neatly into three parts: unity, differentiation and divergence. They even tout a chart explaining their shifting priorities: from credibility at the start to distinctiveness at the end. Sure enough, Lib Dem ministers have used the first days of 2014 to bolster their distinctiveness by skirmishing with their Tory partners. Nick Clegg, the party's leader, has attacked Conservative plans for welfare cuts in the next parliament (see article). Vince Cable, the business secretary, has lavished scorn on "panicked" efforts to deter potential immigrants. This is all part of the plan, Lib Dem aides say soothingly, predicting a controlled divergence before a velvet divorce in 2015. That is unrealistic. Events, not grand five-year plans, have dictated inter-party relations over the life of the coalition. Even during the early "unity" days, clashes occurred over foreign policy, drugs and banking. And just as the past years have defied Lib Dem prognostications of smooth divergence, so the events of coming year may prove disruptively explosive. Senior Conservatives, fairly restrained for most of the past three years, are already talking more freely about favourite bugbears. Under Lynton Crosby, the party's campaign boss, the Tories" tone on welfare and immigration is becoming markedly tougher. In December David Cameron revealed that he keeps a "little black book" of pro-business policies thwarted by his coalition partners. Tory responses to Mr Clegg's carefully calculated provocations were surprisingly volcanic. Boris Johnson, the mayor of London, described him as a lapdog and a "prophylactic protection device." A Conservative adviser was quoted accusing the Lib Dem leader of lying and incompetence. This year's political calendar will pull the coalition parties apart. European elections in May will inflame an ongoing row over Britain's place in the EU. The result (probably triumph for the populist UK Independence Party) will increase the pressure on Mr Cameron to move further to the right. Around the time of the autumn statement the media will interrogate the parties about their post-election fiscal plans. This too could easily descend into an angry battle over the coalition's record: where it has succeeded, where it has failed and why. So divergence will happen without the Lib Dems" help. Their recent provocations, designed to nudge the process forward, are unnecessary. Worse, they raise the risk of a nasty row in the months before the general election, which will damage coalition government, and its Lib Dem boosters, in the eyes of voters. The scratchier the "velvet divorce," the worse their prospects.