Daniel Hannan is an MEP for South-East England, and a journalist, author and broadcaster. His most recent book is What Next: How to Get the Best from Brexit.

As recently as two years ago, the news that Derek Hatton had been readmitted to Labour on the day that seven moderate MPs were forced out would have been seen as proof of Jeremy Corbyn’s utter unelectability. Labour began its journey back to office when Neil Kinnock expelled the Liverpool agitator in 1986. It took another decade, and two more changes of leader, to convince voters that Labour had truly turned its back on communism. But, all of a sudden, we have plunged back down the rabbit hole.

Welcome to the Mad Hatton’s Labour Party. Luciana Berger, whom almost everyone seems to recognise as an amiable sort and a diligent constituency MP, has been driven out by anti-semitic abuse. At the same time, Labour is happy to embrace a man who declared in 2012 that “Jewish people with any sense of humanity need to start speaking out publicly against the ruthless murdering being carried out by Israel!”

Then again, why shouldn’t the old Trotskyist be readmitted? Labour these days is largely led by Trots – although, for reasons that continue to baffle analysts, voters don’t seem to mind any more. Jeremy Corbyn is every bit as left-wing as Michael Foot was, but lacks his predecessor’s charm, intellect and rhetorical ability. More seriously, the Absolute Boy lacks Foot’s patriotism. Foot was one of the few Leftists of his generation who never fell, even fleetingly, for either Mussolini or Stalin. A Leveller at heart, he saw continental authoritarianism as alien to Britain’s radical tradition. Corbyn, by contrast, has yet to come across an anti-British tyrant he doesn’t excuse.

When Leopoldo Galtieri invaded the Falkland Islands, Foot realised that a short victorious war would all but guarantee Margaret Thatcher’s re-election, but he did what he saw as his duty and supported the decision to despatch a military task force. Not so his party’s newly-selected Islington candidate – Corby -, who opposed the war on principle. You might think Argentina’s junta would have been precisely the sort of regime that Corbyn loathed, a military dictatorship that murdered trade union leaders and locked up Left-wing activists. But, no, any distaste he may have felt for one of the few regimes in the world that arguably deserved the favourite Leftist epithet “fascist” was trumped by his conviction that Britain is always and everywhere in the wrong.

Corbyn has not changed a whit during his 36 years in Parliament. But the electorate evidently has. Back in 1983, opposition to Nato and to the nuclear deterrent were seen as disqualifications for office. Now, Labour is led by a man who didn’t just oppose Nato when it counted, but who regrets the outcome of the Cold War. Yet the party is roughly level-pegging in the polls.

Back in the early 1980s, the sense that Labour had become too extreme created space for a third party. The SDP came as close to breaking the Labour/Tory duopoly as anyone has over the past 80 years. Monday’s breakaway, by contrast, was underwhelming. The number of rebels – seven – was smaller than expected. Around 30 Labour MPs had been mulling a split – though, frankly, even that is a paltry number when we consider that 172 Labour MPs passed a no confidence vote in their leader as recently as June 2016.

The seven lack a unifying theme. They don’t like Corbyn, don’t like anti-semitism and don’t like Brexit. Fine. But is that really the basis for a new mass movement? Only the third of these causes has popular energy behind it, but the breakaways’ call for a second referendum has already been undermined by their refusal to follow the Carswell/Reckless precedent and recontest their seats in by-elections (on grounds, hilariously, that more elections would “cause uncertainty”). An opinion poll yesterday showed putative support for a centrist anti-Brexit party at eight per cent.

Psephologists argue about whether the SDP truly kept the Tories in office in 1983. Although the raw figures suggest that the new party took many more votes from Labour than from the Conservatives, we should not assume that the former Labour voters would otherwise have voted for Michael Foot. To do so may well be to confuse cause and consequence. The SDP came into existence at a time when many Labour voters were already feeling disfranchised.

Is the same true today? In a few cases, yes. Most obviously, many Jewish Labour voters have abandoned the party. A handful of Europhiles have also walked away. But what we might have expected to be the single largest bloc – the mass of traditional Labour voters who are looking for a party that is pro-tax-and-spend, but is also tough on crime, patriotic in foreign policy and sceptical about identity politics – has so far stuck with the party. And, as long as those voters do so, most Labour MPs will do the same, letting “I dare not” wait upon “I would” like the poor cat i’the adage.

The Gang of Four caused a split. The Gang of Eight have caused only a splinter. The agonies of Labour moderates are set to continue. And their worst fear – that Corbyn might win – remains real. That is their tragedy. I hope to God it doesn’t become Britain’s.