Defiant Boris Johnson has created a fresh headache for Rishi Sunak by saying he'll provide his WhatsApps and notepads directly to the Covid-19 Inquiry - in spite of Government legal action.
It is a fresh blow to the struggling PM's authority as the row over Westminster's decision to launch a judicial review deepens.
Ministers are worried that allowing Baroness Heather Hallett - who is heading the Inquiry - access to unedited material could cause embarrassment to key Government figures.
It would also set a huge precedent for future inquiries - but Mr Johnson says he's not prepared to become a "test case".
In the latest twist in the long-running saga, Mr Johnson said he will demand his material back from the Cabinet Office so he can hand it over himself if it refuses to do so.
In a letter to Baroness Hallett, the former PM wrote: "The Government yesterday decided to take legal action.
"It was not my decision to do so. While I understand the Government's position, I am not willing to let my material become a test case for others when I am perfectly content for the inquiry to see it.
"I am therefore providing the material directly to your inquiry today in unredacted form."
Mr Johnson said he would ask for his unredacted notebooks back from the Cabinet Office and share them with the Covid inquiry if the Government refuses to do so.
He wrote: "I no longer have physical access to my notebooks because they were removed from my office by the Cabinet Office.
"I have asked that the Cabinet Office pass these to you. If the Government chooses not to do so, I will ask for these to be returned to my office so that I can provide them to you directly."
It is thought allowing Baroness Hallett access to the trove of messages will have huge repercussions further down the line, especially when Mr Sunak's role in decision-making comes under scrutiny.
Baroness Heather Hallett, who chairs the inquiry, demanded un-redacted messages between January 2020 and February 2022, along with ministerial diaries and notebooks - warning officials could face criminal proceedings if they didn't comply.
Ministers resisted the request and, 67 minutes after the crossbench peer’s crunch deadline to surrender the documents yesterday, the Government confirmed it wanted a courtroom showdown.
“The Cabinet Office has today sought leave to bring a judicial review,” it said in a 1,382-word letter to the inquiry.
“We consider there to be important issues of principle at stake here, affecting both the rights of individuals and the proper conduct of government.
“The request for unambiguously irrelevant material goes beyond the powers of the Inquiry.”
Critics said it was "deeply worrying" that Rishi Sunak was prepared to splash taxpayers' cash to try to block the handover of evidence to an inquiry the Government set up itself.
Tory ministers were accused of wasting time by taking the Covid inquiry to court over Mr Johnson’s WhatsApp messages and notebooks.
Former justice secretary Sir Robert Buckland warned it was a “fool’s errand” for the government to take legal action in a bid to stop unredacted documents being handed over.
The Tory MP told LBC: “This judicial review, I'm afraid, is a bit of a fool's errand… I just think this is wasting time and time is not what the victims and those who are really affected by the events of the Covid crisis will want to see being wasted.”
Former Downing Street chief of staff Gavin Barwell said: "Some of the messages might be a bit embarrassing but, nonetheless, I think they're making a bad mistake."
The Tory peer told BBC Radio 4's Today programme that the coronavirus inquiry "isn't about ministers being embarrassed" but about "getting to the truth for all the people who lost loved ones".
He added that "from a timing point of view as well, it's a mistake to prolong this process" by launching a legal challenge.
Their comments came after a Tory minister predicted the Government will lose the legal fight with the Covid inquiry.
Speaking on BBC Question Time, science minister George Freeman said he expected the courts to side with inquiry chair Baroness Hallett, but that he did not think it was a "cynical" exercise and it was a "point worth testing".
