I've thought exactly the same from a very early stage. The outcome will be that 'some gatherings didn't fully comply with the rules, but the Prime Minister was unaware. Boris acted in good faith, and is utterly appalled at the way he was misled'.
For that to work, the public have to believe that Boris was completely unaware of what was happening in his own house. I realise that number 10 isn't your usual 'two up two down' property, but even Dominic Cummings testing his eyesight is more plausible.