Listening recently to a Jeremy Corbyn sympathiser expounding his grievance was both interesting and instructive. Listening is not something at which the political class has had much practice in recent years; although it probably does not realise the fact, its survival now depends on belatedly developing that skill.

Is that a plea for integration of the demented Corbyn agenda into mainstream political thinking? Certainly not. But it is past high time the political class took notice of what is going on among many ignored segments of British life. It is no longer a choice but an imperative, if anything resembling the current political system is to survive beyond 2020.

Dismissing all Corbynistas as “nutjobs” is a self-indulgence that ignores the cardinal rule of politics: try to understand the motivation of your opponents, relieve any legitimate grievances then make an informed refutation of the illegitimate claims. A significant element of the Corbynista insurgency is nothing more than good old-fashioned Trotskyite entryism into the Labour Party, on the Militant Tendency model. But there are other elements that deserve to be studied in a more considered way.

The burden of this Corbyn supporter’s complaint ran as follows. “I believe in socialism. So did my parents and grandparents and the undisputed vehicle for that aspiration was the Labour Party. Then Tony Blair and his associates hijacked the party, removed principle from politics and sought power by courting the lowest common denominator, in electoral terms.” Not many political historians would disagree with that analysis.

“Now we are being told,” he continued, “that if Labour returns to socialism it won’t win an election. So what? We should stand for a principle, win or lose. What’s the point of winning elections if we can’t implement what we believe in? In that case what is Labour for, apart from advancing a few careers? I want to be able to vote for what I believe, whether it wins elections or not. If Labour won’t promote its principles, I have no voice. All the parties represent the same programme. I have no one to vote for. I am disfranchised.”

That was the point where his complaint became identical to that of a UKIP supporter. That is not a flippant point: disfranchisement is the crucial issue that has provoked the present crisis in British politics and which could yet trigger a dramatic revolution in the political system, even beyond what it has already effected.

Consider the almost incredible reality. EU membership was for decades an axiom across all political parties. At the recent referendum – not held due to any democratic instinct among the political class but as an expedient by David Cameron in trying to suppress dissidents within his own ranks – all of the political parties except UKIP (with just one MP) supported Remain. As the result showed, the consensual parties had thereby disfranchised 17.4 million voters.

That is an indication of the scale on which the political class had arrogantly parted company with the electorate. Include other elements, such as the leftists abandoned by Labour, and you can safely add at least 3 million more voiceless voters. Ditto social conservatives, rejected and traduced by the metropolitan liberal establishment, though many of them may also be included within the pro-Brexit insurgency.

The bottom line is that, by any reasonable calculation, the number of voters unrepresented by the mainstream parties on the key political issues exceeded 20 million, out of an electoral roll of 40 million. That is to say, a majority of British voters were disfranchised by the politics of consensus enforced by 650 individuals at Westminster. Could any rational human being have the effrontery to call that democracy?

The scale of the travesty is mind-boggling. To imagine that such an imposture can be sustained any longer is to indulge in fantasy. Yet they are still at it: threatening legal obstacles to Brexit, votes in Parliament to annul the decision supported by the largest number of people in British history, ducking and weaving to water down Brexit, employing delaying tactics.

An entity called “Whitehall” is now claiming it cannot complete Brexit before the end of 2019. Apparently withdrawal from the EU – and withdrawal is always simpler than entry into a commitment – is beyond the talents of all those Five Straight ‘A’s and Starred Firsts in the Foreign Office. If so, they should be sacked and replaced by those with the ability to deliver.

The catastrophe for the political class is that when its imposture was finally blown out of the water by the British public, it was on the issue of EU membership. The EU was the jewel in the crown, the totemic institution to which all the rest of the Consensus was subordinate. With that idol cast down, all the other liberal sacred cows are ripe for slaughter.

It is open season on the consensual political class. Grasping the reality of that existential crisis and bowing to the public will would be the sensible response. But the elite abandoned common sense a long time ago and appears to have lost the basic instinct of self-preservation, making the next four years potentially the most interesting period in politics for generations.

As for the Corbynistas, they will not inherit the earth. Leon Trotsky’s programme is a marketing nightmare. But when the sense of universal betrayal can unite the hard left of the Labour Party with UKIP, social conservatives, Eurosceptics et al., the realisation dawns of just how small a constituency the Consensus had and how selfishly it has misgoverned.