The damage is immense. In retrospect, it seems incredible that Sir Keir Starmer and Angela Rayner thought they could tough it out before establishing the facts.

But they did, and not for the first time.

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So, before we assess this particular case, it highlights a pre-existing nagging doubt. Is speaking without checking a defining pattern of this government?

Tax promises. Welfare cuts. Tulip Siddiq. Waspi Women. The initial winter fuel plan. The vow there would be no winter fuel U-turn.

Even a cast-iron guarantee in July that there would be no reshuffle this month – now there might be three, if you include junior ministers next week.

Each one: an action taken or promise made, combined with fighting talk – before reality dawns and the government retreats into reverse.

Is the word of ministers and their advisers in this government worth less than it should be?

Starmer and Rayner casually tossed untruths

So now this.

For days, two of the most senior politicians in the UK have clutched at factually inaccurate (Rayner) and emotionally charged (Starmer) smears against media reports that are today vindicated, and in doing so, casually tossed untruths into the public domain – even though behind the scenes they were still checking the facts.

The issue hinged on whether Ms Rayner should have paid a lower level of stamp duty on her new Hove flat, because it was her main home, or whether the rate £40,000 higher was due because of her interests in property elsewhere.

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After the Telegraph asked whether she had got it wrong last Friday, her spokesman said on the record she “paid the correct duty” and “any suggestion otherwise is entirely without basis”. Yet later the same day, on Friday night, they decided to check and get a second opinion from a tax barrister.

This led to a change of position from Ms Rayner on Wednesday, and the self-referral to the ministerial standards adviser.

Starmer’s defence

But in the interim, on Monday, while the tax barrister was re-checking the facts, Sir Keir was picking a side.

He attacked critics – who were asking if the housing minister had paid the main housing tax at the right rate – for pursuing a class war.

“Angela has had people briefing against her and talking her down over and over again. It’s a mistake, by the way,” he said.

By this point, No 10 also knew that Ms Rayner was trying to lift a court order which she claims prevented her from going public with the truth. There was no attempt to nuance from the top, however.

Only finally, on Wednesday, on Sky News, did Ms Rayner concede a mistake. The deputy prime minister’s defence was that lawyers had wrongly advised her to pay the lower stamp duty – it was all their fault and she should not be found culpable.

Even this has turned out to be a partial explanation, and that is why she’s gone.

Rayner took a chance

The conclusion by the Downing Street investigator was that she’d ignored clear warnings about her tax bill that she should have followed.

In his adjudication to the PM, Sir Laurie Magnus wrote: “In two instances, [the legal advice] was qualified that it did not constitute expert tax advice and was accompanied by a suggestion, and in one case a recommendation, that specific tax advice be found.”

So she took a chance on not following advice to get a proper tax lawyer, and took a chance a second time by claiming on telly that the advice to her was wrong – and has been caught out only because of media scrutiny.

Ministers take nuanced advice from professionals on a daily basis and have to use their political determination on whether they agree. Something very similar happened here in Ms Rayner’s private life, and she got it wrong.

And at no point did someone in No 10 or her team seek to challenge her explanations before multiple figures mounted a case for her defence in public, of things that proved later to be partial or untrue.

This is the sort of thing that damages public trust: making categorical statements that are untrue because the facts weren’t properly established in advance.

Will lessons be learned across the top of government?