No 10 had issued a mid-morning statement saying Mr Cummings had driven to Durham to get care for his son after his wife falling ill led to “the high likelihood that he would himself become unwell”.
The statement said: “His sister and nieces had volunteered to help so he went to a house near to, but separate from, his extended family. His sister shopped for the family and left everything outside.
“At no stage was he or his family spoken to by the police about this matter, as is being reported. His actions were in line with coronavirus guidelines. Mr Cummings believes he behaved reasonably and legally.”
No10 said the police had not spoken to Mr Cummings or his family, however Durham Constabulary tonight said Mr Cummings’ father had spoken to officers on the phone.
The police statement said: “During that conversation, Mr Cummings’ father confirmed that his son had travelled with his family from London to the North-East and was self-isolating in part of the property.
“Durham Constabulary deemed that no further action was required. However, the officer did provide advice in relation to security issue.”
Soon after the Downing Street statement, senior Cabinet ministers issued statements on social media defending Mr Cumming’s actions as “justifiable and reasonable”.
Michael Gove, the Cabinet Office minister and a close friend of Mr Cummings, said: “Caring for your wife and child is not a crime”.
Rishi Sunak, the Chancellor, said: “Taking care of your wife and young child is justifiable and reasonable, trying to score political points over it isn’t.”
Matt Hancock, the Health Secretary, said: “It was entirely right for Dom Cummings to find childcare for his toddler, when both he and his wife were getting ill.”
And Suella Braverman, the Attorney General, said: “Protecting one’s family is what any good parent does. The 10 Downing Street statement clarifies the situation and it is wholly inappropriate to politicise it.”
Mrs Braverman’s comments could come back to haunt her if Mr Cummings was found to have broken the law.
Several party donors also backed Mr Cummings, including Lord Bamford, the JCB owner, the City grandees Jonathan Wood and Michael Spencer and the property developer Tony Gallagher.
They are understood to have found it “understandable” that Mr Cummings had wanted family support.
Mr Shapps said at the press conference that Mr Cummings would have been thinking about finding “the best possible option” to support his son.
He added: “I would draw this distinction: this wasn’t sort of visiting a holiday home or going to visit someone, this was to stay put for 14 days, to remain in isolation to get over what I understand was quite a significant bout of illness from coronavirus, and then to be able to return to London only when well.”
The scale of backing surprised some former aides with one pointing out that Robert Jenrick, the Communities Secretary, was not given this “level of support” when it emerged he had travelled hundreds of miles to a second home during the lockdown.
A YouGov snap poll found that 68 per cent of people thought Mr Cummings had broken the rules and just over half – 52 per cent – thought he should resign.
The Telegraph understands that some friends of Mr Johnson outside No 10 had sent texts saying he had to sack Mr Cummings “for the benefit of Boris and the country”.
The friend – who claimed he was appalled that Mr Cummings was not more contrite yesterday – said: “This is a car crash. I feel sad for the two of them but the truth is it was the wrong thing to do.
“It is not about Dominic, it is about perception. And when lives matter you may never recover from this.
“If this turns out to be that he stays, there is a public backlash and people say ‘I am going to sit in the park’, and the R rate goes to 1.5 and people start to die again, it could be finished.”
An MP ally of Mr Johnson said Mr Cummings should quit, but probably would not. The MP said the problem was that the people around the Prime Minister felt that they were above the law.
The Conservative MP said: “It is very damaging for the Government because it builds on this belief that there is a genuine feeling in Number 10 that they are above the law.”
In her letter to Sir Mark Sedwill, Ms Reeves wrote: “I remind you of the Code of Conduct for Special Advisers, which states that advisers must ‘comply with the law and uphold the administration of justice’.”
She added: “It is therefore vital that the Government can reassure the public that its most senior figures have been adhering to the same rules as everyone else.
“The British people do not expect there to be one rule for them and another rule for the Prime Minister’s most senior adviser.”