The key thing to bear in mind with the #DominicCummings break of lockdown is the 'mens rea' principle.
"the intention or knowledge of wrongdoing that constitutes part of a crime".

If Cummings and his wife didn't think they were doing anything wrong, they wouldn't have sought to conceal it.

But instead the public were told they were self isolating in London and his wife wrote an article claiming they had
“emerged from quarantine into the almost comical uncertainty of London lockdown.”

So clearly they thought it was important to lie about what they had done, indicating they knew their actions were unjustified.

No amount of retroactively self justifying Signal conversations with Laura and Guido now, can alter the fact that they clearly knew their actions were in contravention of the public guidance.