It sometimes requires one extraordinary, unplanned event to change the dynamics of politics.

For nearly three years, we have reported on the ever-worsening state of Labour’s relations with the Jewish community under Jeremy Corbyn.

This week’s National Executive Committee decision to reject the International Holocaust Remembrance Alliance definition of antisemitism, despite the urgings of 68 rabbis, despite the view of the Chief Rabbi that such a decision would show “unprecedented contempt” to the Jewish community, and despite the demand of almost the entire Parliamentary Labour Party, was another milestone of despair for decent members of the party.

But it received next to no coverage in the non-Jewish media — perhaps a result of antisemitism fatigue. There is, after all, a limit to the number of times one can expect those who are not directly affected by Labour’s embrace of antisemitism to react.

But that one extraordinary, unplanned event has indeed changed the dynamics. Dame Margaret Hodge’s confrontation of Jeremy Corbyn in a corridor of the House of Commons, calling him an “antisemite and a racist”, seems to have burst a dam.

Throughout Labour’s descent into its racist sewer there has been an understandable reluctance in some quarters to confront the appalling reality that the leader of the party, and our nation’s most likely next prime minister, is indeed as Dame Margaret describes him.

This is not about what is in his soul. It is about how he acts. And those facts speak for themselves.

Mr Corbyn has not merely presided over the party’s refusal to tackle antisemitism; he has been responsible for it. He has been responsible for dumping the full IHRA definition, adopted by the NEC in 2016, to be replaced by a definition drawn up specifically to enable Labour members to attack British Jews as having loyalty to Israel above Britain, and to be free to attack Israel as a racist endeavour run by Nazis. 

Dame Margaret has set in train events which cannot be predicted with certainty. But  already Jewish Labour MPs and their allies describe a “civil war” with the Corbynites and say that they are at the “point of no return”.

They cannot back down. The stakes are too high. The racists must not be allowed to win — which means they must be confronted not just with the usual angry words but with action. 

That surely means resigning the Labour whip and forming a new bloc of independent Labour MPs. This week may be the trigger for a revolution in politics.