The Cameroons calculated that grumpy traditionalists would anyway have nowhere else to go. That assumption turned out to be a big mistake. Enter (stage right) Nigel Farage, returning to reclaim the leadership of UKIP after a spell in the background. In 2010 he had stood as a Westminster candidate against the Commons Speaker John Bercow and lost, although not before he was almost killed in a light aircraft crash. He was filmed emerging from the wreckage streaked in blood and the impact left him in severe pain. (Just before Christmas last year he had to undergo a neck operation to alleviate the agony.) 

  

Back in a UKIP leadership role, Farage set about occupying the space vacated by Cameron on the Tories' right flank. Again he was fortunate. The voters' dislike of the political class had bubbled over in the expenses crisis of 2009, when many MPs were found to have been on the take from the taxpayer. Combined with the effects of the squeeze on living standards during a deep recession, the resentment felt about remote elites solidified into cold, hard hatred.

Now pensioners who had saved found their income hammered by the effects of quantitative easing. Hardline Eurosceptics felt they had been betrayed by the Tory leader, who had promised a referendum on the EU's Lisbon Treaty and then not delivered one. Cameron pointed out to no avail that the treaty had already been ratified. Rising concern about mass immigration, and the reluctance of the major parties to discuss it, also aided Farage.

In government, Cameron decided initially that rather than reaching out to alienated conservatives unhappy with the compromises of coalition and resentful about the EU, he would instead redouble his efforts to distance himself from traditional conservatives. The Prime Minister embarked on the legalising gay marriage.

UKIP, then, seems perfectly placed for a breakthrough, to turn three-party politics in England into a four-party system. But all is not quite as it seems. The party, on the eve of its great moment of vindication and triumph, shows signs of having peaked too early.

Having been so exhilarated by the successes of the last year, the party's activists and some of the party's spokesmen talked up their prospects in the low-turnout European elections. It became fashionable in UKIP circles — in particular on the blogs that supporters populate with their comments — to predict first place. However, an ICM poll for the Guardian in February showed UKIP running third on 20 per cent, behind the Tories on 25 per cent and Labour on 35 per cent. This puts Farage only 3 per cent above what UKIP scored in the 2009 European elections.

Although it is possible that a strong campaign — or a Tory blunder — will enable Farage to finish in front of the Conservatives, the party cannot count on floating upwards on an ever-rising tide. It is struggling to attract younger and more moderate voters and it may have hit a ceiling in its support.

Here, the rapid growth in UKIP membership has also brought with it challenges for Farage. Media scrutiny of crackpot candidates has increased and will intensify further. And in recent months the UKIP leader has also showed signs of feeling the strain. Perhaps his phenomenal workrate and neck pain explain his increasing sensitivity to criticism, although it looks as though the old magic may be fading. It did not work for him when he turned up at the recent floods in the south-west of England in waders and a succession of hats. His visit made him look opportunistic and just like all the other party leaders, when his support rests on his standing apart.