Among the series of bombshell revelations about Downing Street’s Covid response, Cummings leaked a screenshot of a WhatsApp conversation purportedly with Johnson that took place on March 27 last year – four days after the first national lockdown was announced.

Voicing concern about the scale and pace of the UK’s testing relative to the US during the early stages of the pandemic, Cummings reiterates that ramping up testing capacity was “integral” to the “escape plan” and criticises “MH” (Hancock) for saying he was “sceptical” about achieving an announced target.

To this, the recipient identified in the screenshot as “Johnson Boris” responds, “Totally f**king hopeless.” Three missed calls follow shortly after that message, which Cummings attributes to Johnson trying to tell him he had tested positive for Covid-19.

In addition, the post contained a number of texts, pictures and documents from emergency COBRA (Cabinet Office Briefing Rooms) sessions that Cummings said would counter the “version of reality” created by “lies” issued from Downing Street and Hancock about their early pandemic response.

According to Cummings, the narrative being spun was that the health secretary had been responsible for the push to increase testing capacity in an “inspired and heroic” effort to “provide leadership.” However, the post noted that Hancock had still been pursuing the ‘optimal single peak’ strategy with herd immunity as late as March 16.

The government’s attempt to “memory-hole” its “Q1 2020 debacle” was analogised by Cummings to a wartime government claiming that its strategy of appeasing Nazi Germany had been a “great success” before pivoting to claim that the “original plan” was to “fight them on the beaches” all along.

Noting that Hancock’s behaviour in April “distracted attention from testing in care homes and the PPE debacle,” Cummings said that the responsibility for “testing, like vaccines, was removed from his control in May because of his incompetence and dishonesty.”

This latest salvo in an ongoing war of words between Hancock and Cummings followed up on the explosive testimony Johnson’s disgruntled former chief advisor gave three weeks ago before a House of Commons committee probing the government’s handling of the pandemic.

Last Thursday, Hancock defended himself against Cummings’ allegations that by delaying the lockdown and other “failures” on testing, care home testing and PPE procurement, he had cost “tens of thousands” of lives to be lost needlessly.

Of that performance, Cummings, who had a falling-out with Downing Street last November, said, “Hancock gave a fictitious account... and portrayed himself as a heroic figure who had been in agreement with the PM throughout the crisis.”

Naming Hancock as directly responsible for such key roles as dealing with Covid variants was a “guaranteed disaster”, and Cummings said his removal was a matter of “public safety”.

Much of what was published in the blog post related to documents Cummings had been asked to hand over to the committee prior to Hancock’s testimony. However, he did not meet the committee’s deadline for submitting them.

When approached by the BBC, Downing Street stated it did not deny the authenticity of the messages. However, the PM’s official spokesman told the broadcaster that “Mr Johnson has full confidence in the health secretary.”

Other charges Cummings hurls at Johnson include telling “rambling stories and jokes” during emergency meetings, “encouraging ministers to give false accounts to Parliament” and apparently planning to leave office after the next election in order to “make more money and have fun.”

Noting that the parliamentary inquiry would not hold Johnson to account, Cummings wrote, “If No 10 is prepared to lie so deeply and widely about such vital issues of life and death last year, it cannot be trusted now either on Covid or any other crucial issue of war and peace.”