Lord Pearson of Rannoch, elected leader of Ukip yesterday, is the first peer for a century to lead a political party. More significant, I think, is the fact that this is the first time for decades that a minor party has been led by a politician with deep roots in the British establishment – and formidable campaigning skills honed inside rather than outside the Palace of Westminster.

I came across Malcolm Pearson seven years ago, when I was working on an investigation for this newspaper into the BBC’s grotesque propagandising on behalf of the EU and the euro. Pearson, then a Tory peer, had sent a series of letters to senior BBC executives, naming instances of bias and pointing out precisely how they compromised the corporation’s charter obligations. These letters caused havoc at White City, not only because they came from the House of Lords, but also because Pearson had judged his tone and targets so carefully. They were a major factor in the BBC’s reluctant decision to give more air time to Eurosceptic arguments.

This morning David Cameron will be rejoicing, understandably, at the YouGov poll that shows him capturing northern marginals. But I’m sure he is displeased by the election of his fellow Old Etonian Pearson, who not only knows the Tory heartlands like the back of his hand, but has decided to launch a campaign against uncontrolled immigration and radical Islam that will resonate powerfully in those northern marginals.

You may think that Ukip’s new focus on the Islamification of parts of Britain is a dangerous strategy. And so it would be, if the party was in other hands. But Lord Pearson is still essentially a libertarian Tory: he would never stoop to sending out dog whistles to wavering BNP racists. His campaign against uncontrolled immigration and Sharia will be rooted in a defence of liberal democracy of the sort that other parties are too gutless to make.

The arguments against voting UKIP are still strong: Pearson wants to force a hung parliament, which would be a wretched result, since it would hand power to that most opportunistic of minority parties – the Lib Dems – rather than produce the realignment of British politics that he envisages. But Pearson still has (very) highly placed friends within the Conservative party, and if his presence on its borders can force the Tories to pay closer attention to public opinion on immigration and Europe, then he will have done us all a favour.