Of all the party’s factions, Labour First was the most practical. It wasn’t filled with rosy-cheeked Blairite missionaries from the upper-middle class, or with Corbynites who had never recovered from their first reading of Lenin as the joints were passed around in the 70s.

Working class and hard headed, the Labour First rally at last year’s conference echoed to calls of “stay and fight” Corbyn. Show-offs would walk away, “hawking their conscience around from body to body asking to be told what to do with it”, as Ernie Bevin, hero of old Labour’s right, put it. Real Labourites would do the hard work to recapture the party from the far left.

A dissenting note sounded in a Black Country accent. “You say we must stay and fight,” said Ian Austin MP. “But where is the fight? When will it happen?” The fight could never be won, he concluded last week. I spoke to him the day before he resigned the whip and could hear the tension and sadness in his voice. His words will stay with me. The “fragility” of British institutions horrified him. If someone had told him the Labour party of Bevin, which founded the NHS and Nato, could be led by Jeremy Corbyn, dominated by Seumas Milne and Andrew Murray from communism’s Stalinist wing, while also being infected with antisemitism, the conspiracy theory of fascism, he would never have.... You can guess the rest.

Fear about the fragility of Britain is cracking the old parties. Everyone is concentrating on the politicians who, like Austin, have resigned. Theresa May and Corbyn would do well to worry about the MPs they have left behind. Many look at Austin, Anna Soubry, Chuka Umunna et al and notice they are like prisoners who have thrown off their chains. They are finally free to say what they think and freedom is infectious.

Walk in the shoes of a disaffected backbencher. Women MPs are almost physically sickened by the treatment of Luciana Berger. She did her best. She tried to accommodate herself to the far left and worked in Corbyn’s shadow cabinet. No good did it do her. The left turned on her as it will turn on any Jew who will not parrot the party line. Her chief enemy, and chair of her constituency party, was one Alex Scott-Samuel, a conspiracist who appeared on David Icke’s platform to babble about the Rothschilds “being behind a lot of the neoliberal influence”. Yet it is Berger who is driven out. Scott-Samuel stays with Corbyn and John McDonnell’s blessing. It’s their party now and for as far ahead as anyone can see.

Mike Gapes, another politician from the heart of the Labour movement, told me his former sisters had been thanking him because he made a stand against Berger’s abusers when he quit Labour. What have they done? Fired off a couple of angry tweets, maybe? Once, that might have been enough, but the existence of a breakaway movement changes everything. Suddenly, their protests seem inadequate compared to their colleagues’ grand gesture.

“The people who left were bold, brave, principled and honest,” one Labour politician told me with a deep sigh. She’s staying for now and will only resign when she can join a movement with a realistic chance of changing Britain for the better. Staying and fighting: that slogan again.

The people who left were bold, brave, principled and honest

But what if the fight is lost and a century of Labour history has ended with the triumph of the communist tradition over social democracy? Those who stay must see there’s little recompense for loyalty. May has never made concessions to one-nation Tories – only to the right. Corbyn and McDonnell have offered nothing to the millions of Labour voters who worry about racism or demand that Labour fights Brexit. If Corbyn breaks his promise on a second referendum or, more characteristically, pretends to support a people’s vote while quietly sabotaging it, more MPs will go. There’s talk of Tom Watson, the nearest the modern Labour movement has to a Bevin, forming a real Labour party. Whether it’s more than talk, I can’t say. One thing is certain, the question “do you think Jeremy Corbyn is fit to be prime minister” has the same answer it always had. I don’t know how much longer the bulk of the parliamentary Labour party can avoid delivering it.

I am glad to see the John Humphrys/Daily Mail view that politicians are venal time-servers is taking a deserved pounding. The best politicians are throwing away their careers, and speaking without fear. Soubry described meeting May and realising she would risk the economy because of “her problem with immigration”.

Berger described how Corbyn had not met her since 2017, even though the criminal justice system was dealing with racists who had threatened her. They were speaking with the moral authority of whistleblowers and looked like free women as they did it. Do not underestimate how many politicians envied and wanted to be them.

Bevin was attacking George Lansbury, a pacifist and the most leftwing Labour leader before Corbyn (although in every respect a more decent man), when he denounced “hawking” of consciences at the 1935 party conference. He wasn’t just crying in despair but following a clear strategy. Once the unions disposed of Lansbury, Clement Attlee could become leader and Labour would be ready to fight fascism.

Today, there is no hope of success for Labour MPs and supporters who want to stop it becoming an antisemitic, anti-European home for creepy fanatics. The cause of Tories trying to stop their party becoming a blue Ukip strikes me as equally hopeless. It’s all very well condemning virtue signalling and preferring those who stay to do the hard, unglamorous work of reclaiming their parties. But these are times when our conscience is all we have left.

• Nick Cohen is an Observer columnist.