The right, as well as the left, is home to the kind of flaming conspiracy nut who, in Bertie Wooster’s words, make ‘strong men climb trees and pull them up after them’.

In another life, the activists for Vote Leave might have joined the thousands of hollowed-eyed onanists who post abuse under newspaper articles from their parents’ spare rooms, or become columnists for the Mail; fringe figures, best ignored.

But just as on the left of politics the fringe is becoming the mainstream, so on the right, brooding paranoids, who cannot face a hard fact or uncomfortable argument squarely, are moving in to take over the Conservative Party.

Vote Leave is not a fringe organisation, like UK Against Water Fluoridation, or The Society for the Propagation of the Gospel in Foreign Parts. The Electoral Commission decided in its wisdom it was respectable enough to lead the official Brexit campaign. Whether it is Michael Gove or Boris Johnson, a Vote Leave politician will be the next leader of the Conservative Party one way or another, and hence our next Prime Minister. The darkness on the right of politics is about to cover the land, and it is worth peering into the murk before it descends.

Look at the email Vote Leave sent to journalists, after ITV said it would host a debate on Europe between David Cameron and Nigel Farage, and get a taste of what is to come. In one statement, it showed every facet of the paranoid mind.

First Vote Leave played the man rather than the ball. ‘ITV is led by people like Robert Peston, who campaigned for Britain to join the euro,’ it spluttered. Then the right imitated the far left and said all the broadcasting rules and impartiality codes ITV must follow were a sham; a whited sepulchre that hid the plots of designing men. Far from being impartial, ‘ITV have [sic] effectively become part of the IN campaign’.

As well as being dishonest, ITV was mendacious. For Vote Leave maintained, ‘ITV has lied to us in private, while secretly stitching up a deal with Cameron to stop Boris Johnson or Michael Gove debating the issues properly.’

In a ‘you haven’t heart the last of this’ conclusion, Vote Leave slammed the door and departed with a threat, which would once have sounded as absurd as Lear raging against the storm, but now sounds horribly plausible.

“ ‘There will be consequences for its future – the people in No 10 won’t be there for long.’

Its threat to independent journalism is Putinesque: bend the knee or you will pay. And it is a telling coincidence that only a few days ago Johnson was whitewashing Russian imperialism in the Ukraine.

I will not bother going through the Vote Leave statement line by line, for it is pointless trying to reason with the demented. I suppose I should say, just to cover The Spectator legally, that Robert Peston did not campaign for the Euro and no sane person doubts his impartiality as a broadcaster.

Instead, I want to talk to sensible Conservative politicians, journalists and voters, assuming any still exist.

For years, I and people like me from the left warned about the darkness growing on our side of politics. We were not just ignored, but denounced by supposed moderates from Gordon Brown to New Statesman hacks. They did not want to admit any fault on the left. They did not want to criticise anyone on ‘their’ side.

Look now at the pass their cowardice and complacency has brought them too. The far left has taken over their party. It is guaranteeing right-wing rule, whoever the Conservatives pick as their next leader, and however badly the Tories behave. It is not just the years of opposition that stretch ahead to the horizon that should shock them.

They have dishonoured themselves. The decade-long failure of left-wing commentators and politicians to speak out has made them look worse than fools, it has made them look like collaborators.

I am sorry to sound like an Old Testament prophet, but the same fate awaits Conservative politicians and commentators who bite their tongues now. If you stay silent while the independence of ITV, the BBC and Channel 4 is attacked, because you think that ‘Boris is a good guy at heart’ or ‘it’s our job to attack the left not the right,’ the future will judge you. And I doubt it will be kind.