Here's the view of Kirsty Brimelow QC of Doughty Chambers as to whether Cummings broke the law and ignored government guidelines.
She states
"the legal position is that the Regulations were introduced for “preventing, protecting against, controlling or providing a public health response to the incidence or spread of infection or contamination” (section 45C(1) of the 1984 Act).
How does the movement of potentially infectious persons around the country comply with purpose of the Regulations ?"
Also
"Deputy Chief Medical Officer, Jenny Harries said that being in a car for hours means that there is a "higher risk" of infection. If Mr. Cummings's wife was displaying signs of Covid-19, sitting next to her in a car for hours would have increased the risk of spreading COVID-19 in his household (as opposed to staying at home and following NHS guidance on distancing in the home).
And as to the potential need for someone to care for their child, it is important to consider whether there were family or friends near his home in London who were able to assist if required? They may not have been first choice but the pandemic and emergency laws passed in response to it introduced restrictions on all of us doing what we would prefer."
She concludes
"Currently there are questions to be answered as to how Mr. Cummings says that he acted legally.
Indeed, unlike all those people who have been prosecuted to date, Mr. Cummings' household actually did have COVID-19.
As to the responsibility of his actions, it is completely clear that Mr. Cummings breached government guidance which is presumed to be responsible.
Whilst the strategy of attempting to argue that Mr. Cummings' conduct was within government guidelines is insulting and distressing to those who have made terrible sacrifices by staying indoors away from family, it also clears the "we're all in this together" smokescreen to reveal a political plane where different rules apply."
It really is not adequate for the PM to just assure the public that the law was not broken, without entering fully into the specifics of what has happened.
https://insights.doughtystreet.co.uk/post/102g80l/did-dominic-cummings-act-responsibly-and-legally