Surely, and at long last, the moment of truth is near for the Parliamentary Labour Party. Yet again displaying their profound unhappiness with Jeremy Corbyn, Labour MPs voted by 169 to 34 on Tuesday to reinstate elections to the Shadow Cabinet so that they, and not the leader most of them loathe, can decide the party’s front bench team.

Good for them, would be the opinion of most people who want to see the British Labour Party at least shaping up to be a proper opposition once again, and not the plaything of Hard Left entryists.

The trouble is that the PLP’s victory may be very short-lived because the change back to MPs electing the Shadow Cabinet, or Parliamentary Committee to give it its Sunday name, has to be ratified by two bodies who could very well give the MPs another bloody nose. The first is the party’s ruling National Executive Committee, an outfit increasingly influenced by the Corbynistas, and then by Labour’s national conference, due at the end of this month in Liverpool.

If either, or both, reject the MPs’ demand can it really be very long before the majority of Labour MPs decide that enough is enough and summon up the courage to leave Corbyn and his less-than-merrymen to their own devices and form a proper centre-left party? A party moreover that might stand a chance of winning something someday.

In the interests of parliamentary democracy in this country they must.

We’ve been here before, of course. It is thirty five years since Labour’s last split but this time the numbers are massively on the side of the moderates. This would make a breakaway much more significant and give it a much better chance of success.

On Sunday January 25, 1981 “Find the Gang Of Four” was Fleet Street’s order of the day. Yes, the splitters then were very significant figures – Roy Jenkins, former deputy Labour leader, ex Chancellor and Home Secretary, David Owen, former Foreign Secretary, Shirley Williams, ex Education and Prices Secretary and Bill Rodgers, former Transport Secretary. But, still, they were only four and in spite of the sizeable political earthquake that they subsequently caused they attracted only 28 more Labour MPs (and one Tory) to their banner.

That time round Labour’s special conference at Wembley on Saturday January 24 1981 had proved the final straw for the Gang – or at least provided them with the best excuse for their long-planned breakaway. There Michael Foot’s ineffectual leadership had been exposed as the party, dancing to a tune composed by Tony Benn, swung significantly to the Left. Control of leadership elections was passed to the trades unions and Labour set its face firmly in favour of unilateral disarmament and against EEC ( as it then was) membership.

There was no doubt that the Gang would ‘break the mould’, to use ‘Woy’s’ favourite expression, and split with Labour in the aftermath. The question that dreary Sunday morning was when would they do it and where would they announce it?

The hunt for the gang’s hideout took me first of all to Bill Rodger’s Islington home. It was the obvious place to try as that’s where much of the pre-Wembley plotting had taken place over Silvia Rodger’s dinner table.

But the birds had flown.

Narrow Street in rapidly Yuppiefying Limehouse was my next port of call – the Owen residence. And here they were. After what seemed like an eternity, this “doorstep” revealed all. Out came the Gang to pose for pictures and issue what became known, rather portentously, as the Limehouse Declaration and the establishment of the Council for Social Democracy (or as Dennis Skinner very quickly re-dubbed it – the Council for Social Diseases).

It is hugely illuminating to consider how that now forgotten document, which presaged the formal launch of the Social Democratic Party three months later, bears on current events. Does it not have a message for present-day Labour MPs? In states that the leftwards lurch at the Wembley conference had been “the culmination of a long process by which the Labour Party has moved away from its roots in the people of this country and its commitment to parliamentary government.”

But if that’s too vague for today’s PLP majority, how about this from the Gang of Four three and a half decades ago:

“We recognise that for those people who have given much of their lives to the Labour Party, the choice that lies ahead will be deeply painful. But we believe that the need for a realignment of British politics must now be faced.”

The breakaway was painful then – the SDP is still held responsible for splitting the anti-Thatcher vote in the 1980s – and it would be painful for long time Labourites now. But how much humiliation are they prepared to accept? Surely, if their latest demand for a Shadow Cabinet elected by MPs is rejected by the Corbynistas on the NEC and at conference they must accept that they’ve come to the end of the road.

By a massive majority in June – 172-40 – they expressed their complete lack of confidence in Jeremy Corbyn and signalled that under him Labour is going nowhere. A realignment on the left and centre-left is theirs, and Britain’s, best option. If they’re defeated in this latest tussle with Corbyn the vast bulk of Labour MPs must see that it’s their only option?