Tonight’s episode of Panorama will be met with two distinct reactions among Labour Party members. There will be those who watch it in utter horror, left feeling sad and hurt, and by 10pm they will be wondering if they want to continue belonging to their party.

And there will be those will bluntly dismiss it as BBC propaganda – a desperate intervention by the state to undermine Labour just as the prospects of a snap election increase.

It’s clear which group Jeremy Corbyn’s closest allies will be in.

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One party source told a newspaper: “With a possible General Election around the corner, this smacks of bias and interference in the political process by the BBC and a clear breach of their own editorial guidelines.”

It’s disheartening, and yet unsurprising, that this was someone’s first reaction to being told that the BBC’s flagship investigative journalism programme has felt justified in posing the explosive question, ‘Is Labour antisemitic?’

There is something rotten at the heart of the Labour Party.

Back in 1985, Neil Kinnock warned of a party being so out-dated and misplaced that it ended in the "grotesque chaos of a Labour council – a Labour council – hiring taxis to scuttle round a city handing out redundancy notices to its own workers".

Now we’re witnessing the grotesque chaos of the Labour Party hiring expensive lawyers to scuttle around and hand out legal letters to its own former workers.

Trying to use non-disclosure agreements (NDAs) against ex-employees who contributed to Panorama is an extraordinary overreaction.

It is also the height of hypocrisy given Labour’s campaign to stop NDAs being used to gag whistleblowers.

Just over two years ago, Shadow Attorney General Shami Chakrabarti argued in a newspaper article that whistleblowers keep us safe and must not be silenced. Her views were shared on Twitter by none other than Jeremy Corbyn.

Too often in the Party of Workers, it seems the party’s support for workers doesn’t apply to its own workers.

From a PR perspective, the legal letters are also a disastrous own-goal for Labour.

They gifted the Sunday newspapers a political row, days before the BBC even began its own PR operation to promote the show.

As a result, a wider audience of voters is now aware of the latest antisemitism crisis to engulf the party – even if they don’t tune in tonight.

And yet I suspect those surrounding Mr Corbyn just don’t care. They appear keener to talk up nonsense conspiracy theories than tackle racism in the party, and keener to deselect anyone considered a ‘Blairite’.

Meanwhile, more and more members quit, and more and more voters turn their backs on Labour.

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Clearly, the party should be streets ahead in the opinion polls right now, not languishing as low as 18 per cent.

It’s little wonder, therefore, that even those once closest to Mr Corbyn have perhaps finally realised that his project is failing.

According to weekend reports, denied publicly, Shadow Chancellor John McDonnell and Shadow Chancellor Diane Abbot warned Mr Corbyn that he must enthusiastically back a people’s vote on Brexit and clear out some of his top team, or face a leadership crisis.

When Neil Kinnock battled Militant, the hard left did not have control of the party.

Today, with General Secretary Jennie Formby, Mr Corbyn’s chief of staff Karie Murphy, Unite leader Len McCluskey, and chief spinner Seumas Milne – among others – it does.

Most party leaders, after their initial honeymoon ends and critics become more vociferous, tend to retreat into a tight leadership circle of unquestioning allies who share the same beliefs. That is what is happening now at the top of the Labour Party.

It’s why Emily Thornberry has been ostracised, and John McDonnell feels bold enough to express exasperation with Labour’s Brexit policy.

It took Scottish Labour leader Richard Leonard just hours following the European election humiliation to recognise that a change of policy to back both a people’s vote and remaining in the EU was necessary.

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The party in Scotland has yet to demonstrate it truly means it – there is still no sign of a summer campaign to take on the SNP and the LibDems. Where are the set-piece speeches, the leaflets for activists, or the social media videos? But at least it’s there on paper.

As for UK Labour, the switch to a policy position supported overwhelmingly by the party’s voters and members has been painfully slow.

According to insiders, Mr Corbyn’s Euroscepticism could have been overcome months ago if it wasn’t for the three ‘Ms’ standing in the way – Murphy, McCluskey and Milne.

The guiltiest party in that trio is surely workers’ champion Len McCluskey, who is so determined to back Brexit he has forgotten that he is supposed to represent workers.

What a disgrace to the proud trade union movement, with all the other major unions long since recognising the need to fight Brexit for their members.

But Monday’s decision by union bosses to back a referendum on any deal brokered by the Tory government or a no-deal exit from the EU has finally paved the way for a change of heart at the top of the party.

Yesterday, members received an email from Mr Corbyn announcing that Labour would campaign for Remain if there is a new referendum on a Tory Brexit or no-deal – although, tellingly, the email doesn’t spell out what Labour would do if it managed to secure its own deal.

Labour is now the ‘party of choice’ when it comes to Brexit, the leader told the BBC.

Why on earth did this take so long?

While Mr Corbyn prevaricated, it fell to deputy Tom Watson to step up and do what the leader should have done months ago.

Nobody has done more to stem the flow of MPs, members and voters into the arms of other parties than Mr Watson.

He understands that Labour only wins when it is a broad church, and attempts to purge the party of ‘Blairities’ will simply lead to continued Tory rule.

And he led the internal campaign to make Labour a pro-Remain party once again.

That battle has now seemingly been won, but what cost has this perfectly avoidable delay had on Labour’s electoral fortunes?

And there is still one major challenge that remains. Will voters believe Jeremy Corbyn?

They have absolutely no reason to do so.