Yesterday's response from Labour welfare secretary Pat McFadden to this newspaper's publication of the McSweeneyGate emails - which revealed how Keir Starmer's most senior aide tried to hide a secret 'Slush Fund' from the electoral watchdog - was instructive.

'Morgan is a highly talented individual,' he claimed.

'I'm not surprised the Tories are targeting someone like that. They'll see him as a formidable opponent, who worked with me to deliver the biggest Labour victory for a long, long time.'

There was no attempt to address the detail of the revelations, save for an airy dismissal they had already been looked into. And there was conspicuously little replication of Starmer's pious entreaties over the need to maintain the highest levels of conduct in public life.

Morgan McSweeney had helped Keir Starmer into power - and that was all that mattered.

This morning, Downing Street officials are fervently praying the developing crisis over the Prime Minister's most loyal and ruthless consigliere will pass. They hope, in the words of one Labour MP, 'that people will think it's just more Westminster double-dealing, and doesn't matter'.

It won't pass. And it does matter. For the following reasons.

First, Morgan McSweeney is not just another political bag-carrier. He is the most powerful figure within the Government - including Keir Starmer. As one minister told me: 'People call him the real Deputy Prime Minister. They're wrong. He's the real Prime Minister.'

Sir Keir Starmer and his Chief of Staff, Morgan McSweeney - arguably the most powerful figure within the Government

And he breached the law. The organisation he directed, Labour Together, was fined £14,000 for failing to declare £750,000 of donations.

But that wasn't all he did. When the Electoral Commission opened an investigation into the suspected breaches, McSweeney was obliged to engage openly and transparently with the its investigation. And he didn't.

As the emails published yesterday revealed with devastating clarity, McSweeney obfuscated, deflected, misled, misrepresented and distorted the truth in an attempt to throw the watchdog off the scent - to the extent that his own lawyer was forced to declare: 'My concern is that unless you are able to help with the questions I pose below, we probably should not refer to you at all.'

McSweeney wasn't able to help with the questions. And he still isn't helping. Why, as the emails stated, were his lawyers afraid of raising the commission's suspicions? Why did his lawyers feel the need to try to hide his involvement in the scandal at all? What did they feel they had to be 'careful' of? We still await the answers.

There is a second reason this matters. Without McSweeney - and Labour Together, the secretive lobbying group he masterminded - Starmer would not be in Downing Street.

Yesterday, as the storm broke around them, Labour Together ran for cover. 'Neither Keir, nor his leadership campaign, accepted monetary or in-kind donations from Labour Together during the leadership election,' a Labour source claimed.

But that claim is false. Labour Together was the vehicle Sir Keir used to transport him to the party leadership. It is a matter of documented fact the group provided polling for him and set the strategic direction for his campaign. As one former member of his team admitted yesterday: 'Morgan basically ran Keir's leadership campaign.'

And McSweeney and his allies didn't even try to hide the fact. In the book Get In, a detailed chronicle of Starmer's ascent to the premiership, a 'friend' of McSweeney provided an infamous quote. 'Keir's not driving the train. He thinks he's driving the train, but we've sat him at the front of the DLR.' That is, the Docklands Light Railway, the east London train network that famously has no drivers.

I was told by a minister that when Starmer saw that quote, he 'hit the roof'. At the time, I thought it was because he felt legitimate anger that own allies were painting him as McSweeney's puppet. But in the context of the new revelations, it takes on a more significant meaning.

Over the past couple of days, Westminster's focus has been on McSweeney's failure to disclose donations to the Electoral Commission. But mounting evidence is emerging of another breach of the political rules Starmer has consistently professed to hold so dear. In the wake of his leadership campaign, he was obliged to place all donations - including 'in kind' donations - in Parliament's Register of Members' Interests. And there is no entry for Labour Together.

Without McSweeney and Labour Together, British politics would have been markedly different. So Starmer's attempt to suddenly distance himself from McSweeney and his organisation stretches credibility to breaking point.

And there is a third and final reason this whole tawdry affair matters: because Keir Starmer told us so. It was he who repeatedly lectured the Tories - and the nation - on the need to clean up public life. It was he who berated Boris Johnson time and time again over any alleged ethical breach, however small. It was he who self-righteously declared: 'Labour will end the chaos of sleaze.'

Now those words are coming back to bite him. And those who piously did his bidding.

Labour Together - an organisation once directed by McSweeney - has been fined £14,000 for failing to declare £750,000 of donations

The lawyer who advised McSweeney that it was best to put his Electoral Commission subterfuge down to an 'administrative error' was Labour's own counsel, Gerald Shamash. The same lawyer who in 2022 imperiously wrote to the Metropolitan Police demanding an investigation into who paid for Boris Johnson's No 10 wallpaper.

'It is respectfully suggested that the known facts and the clear, sensible inferences to which some of those facts give rise create such reasonable suspicion that, were the suspect anyone other than the Prime Minister, the Metropolitan Police would rightly consider itself duty-bound to investigate,' Shamash stated in his leaden, lawyerly prose.

But the scandal enveloping McSweeney, Labour Together and Starmer is not about home furnishings. It's about something far more significant: the man in Downing Street, nominally taking the decisions that affect every one of us - and the extent to which his path to power was funded by an illegal political slush fund.

This morning Keir Starmer is sitting behind the curtains of that historic building, trying to hide. From the Electoral Commission. From Parliament. From the police.

But he is not going to be able to hide. Because this scandal is not going to go away. When he entered office, the Prime Minister pledged to bring transparency and integrity back into British politics. And whether he likes it or not, his opponents are about to hold him to his word.