I have great sympathy for the situation he found himself in.
I despise what I know of him and his utterly disproportionate role in policy making given he is an UNELECTED advisor/"official", plus his part in the architecture of a lavish lying culture as executed by Boris.
I see the two as different entities and should be judged as such. You cannot hate someone's actions just because you hate them in this scenario. You have to weigh everything out and scale it down to very simple facts.
Did the 30 mile drive break any rules? On the edge of the line I see, probably not, He was 15 days into isolation, he wanted his wife there because he wanted to be sure he could make it, his kid was with them most likely because alternatives were not necessary. They distanced and bothered no-one.
Is it feasible that he would panic and make the 270 mile drive due to worries over his (autistic?) son? Absolutely. A legitimate for given everything, a very human one too ("human" not being a trait he has publicly displayed much, but again, that is irrelevant).
Is it feasible he drove non-stop to his father's estate, thus impacting no-one directly? Absolutely, and I actually believe him.
Was his behavior selfish and oblivious? I believe so. Yet I am not prepared to say, with any degree of honesty, that had I been in that exact position I would not have done the same.
Did he break a rule in doing so? Technically yes. He did. He should, by the letter of the rules in place, have immediately sheltered. Concerns for children are a factor, but technically, there wasn't one at that point. I would speculate that a less oblivious person might've assumed that the possibility of covid19 was large in previous weeks given Johnson's reckless behavior. I would speculate that he could've got somebody in place to help with his kid at that point, doubtless like many might've had to do.
And here's the kicker, the BIG difference between Cummins and me, you, the general public. He is a major policy maker/influencer who is in a position of enormous importance and leadership. Again, I am keeping my own personal views about this off the table...the fact remains that in his current role, he needs to be a leader who holds himself to the highest standards. He cannot have it both ways. He cannot be involved in policy-making and running the country and then discharge the extra responsibility which comes with it.
So breaking it down, in my view, he has been felled by TKO in the 9th. His arrogance/obliviousness/attitude/whatever has not aided his case or cause, but again, being a clam does not mean someone is always technically wrong. In this case, I'd say sadly that both apply.
If he cared about the country and the party who employs him, he would step down. He clearly doesn't. And Boris the Clown clearly knows that his PT Barnum Ringmaster as imagined in a cheap PG Wodehouse book act is NOT going to cut it when proper governance is needed.
As a side note, I wonder if Cummins is a bit autistic? His press conference suggested someone who genuinely does not seem to understand why people are tinkled off.