Conor Burns, one of the troupe of Johnson loyalists willing to humiliate themselves on behalf of the prime minister, now knows the first line of his obituary. It will be his attempt to excuse Boris Johnson’s lockdown-busting birthday party inside Number 10 with the immortal phrase “he was, in a sense, ambushed with a cake”. This deserved all the mockery it got, but it is by no means the most desperate of the arguments being offered by those trying to save the prime minister’s skin.