Carrying a box of belongings, the controversial aide marched out of No 10, briefing allies that he was gone for good – although it is understood that he will actually carry on working for another month.
The bizarre photo-op was staged after a week of turmoil and bitter infighting that saw the prime minister’s confidence in Mr Cummings apparently drain away.
It is reported that Mr Johnson wants to “clear the air and move on” after the departure, with suggestions the PM accused Cummings and his close ally Lee Cain of being behind recent negative briefings.
Further reports suggest Cummings was told to “get out and never return” following a 45 minute explosive meeting in Downing Street.
It comes as No 10 has bowed to MPs’ pressure to appoint a chief of staff, to bring discipline to its operation, after the extraordinary disorder and upheaval of recent days, triggering Mr Cummings’ demise.
The role will be taken on temporarily by Edward Lister, a trusted aide from Mr Johnson’s days running London “pending a permanent appointment to the post”.
In a day of confusion, Downing Street first refused to say if Mr Cummings had formally quit or whether he will sever all ties, amid a suggestion that he could even retain a ‘hot desk’.
The later, furious briefing over his departure date pointed to a fresh clash and a possible attempt to force him – and Cain, the former No 10 communications chief – to work a notice period.
A No 10 source insisted: “Dominic Cummings and Lee Cain will continue to work for the PM and No 10 until mid-December.”
Alternative versions of the final meeting between Boris Johnson and his aides soon surfaced, with some reports suggesting that the prime minister had angrily ordered the pair to “get out and never return” after accusing them of briefing against him and his partner Carrie Symonds.
Another version of the alleged “showdown” claimed the trio had shared jokes and posed for pictures.
Nevertheless, the departure brings down the curtain on Mr Cummings’ extraordinary central role at the heart of power, after being credited as the campaign genius behind the Brexit referendum victory.
Michael Heseltine, the pro-EU former Conservative deputy prime minister and now the president of the European Movement, said: “In an interview in March, I forecast Dominic Cummings would be gone by Christmas.
“I can think of no man who has done so much harm to this country, in so short a time. He has left a generation to pay the price of Brexit.”
Tory MPs – who credit him with the twin triumphs of the 2016 referendum and the 2019 general election campaign – also spoke of the need for change.
Theresa Villiers, the former environment secretary, attacked his “dismissive attitude” to ministers and MPs” saying: “This is an opportunity to move on from that and to have a more collaborative approach.”
Bernard Jenkin, who chairs the Commons Liaison Committee, welcomed an opportunity to restore “respect, integrity and trust” that had been “lacking in recent months”.
“It’s an opportunity to reset how the government operates and to emphasise some values about what we want to project as a Conservative Party in government,” he said.
Arguing that “no prime minister can afford a single adviser to become a running story”, Sir Bernard added: “I’m not surprised in a way that it is ending in the way it is. Nobody is indispensable.”
And Roger Gale, another Tory MP, called for a powerful chief of staff, saying: “Frankly, this is a distraction that cannot and should not be allowed to take place, and the prime minister has got to get a grip on it.”
A senior MEP also expressed optimism that a no-deal Brexit deal was now less of a danger, with the hardline Mr Cummings going, but the suggestion was quickly stamped on by Downing Street.
Mr Cummings’ departure was “probably the sign that Johnson has begun his U-turn and will in the end accept EU conditions” for a trade deal, said Phillippe Lambert, who sat on the European Parliament’s Brexit committee.
But the claim was rubbished by the prime minister’s spokesman, who said: “Absolutely not. That is simply false. The government’s position in relation to the future trade agreement negotiations is unchanged.”
The negotiations remain deadlocked, ahead of an EU deadline of next Thursday, when it is believed Brussels could make a “take-it-or leave-it” offer.