I HAVE seldom witnessed in politics a more shameful episode than the Cummings affair. I’ve always thought Boris Johnson unprincipled and mendacious. But, when I watched him at his press conference, I was appalled – especially by his claim that Dominic Cummings followed his “instinct as a father”.

It was to misunderstand, deliberately, the questions being asked of him. All of us have an instinct to be with, protect, and care for those we love. We’ve been putting aside that instinct, however, because we accepted that our sacrifices have been for the common good.

My own mum is in her 90s and in a respite home following a protracted stay in hospital. She is desperate to get back to her flat. She is even more desperate to see her two sons. Despite this, for these long weeks, I have been unable to visit and now the nurses tell me that she has stopped eating and seems deeply depressed. I feel a huge sense of responsibility, and I feel too that I am letting her down, even though I know I have no other choice.

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This is not an issue of right or left. It’s a matter of justice. I try not to be a tribal politician after many years as a journalist where my personal allegiances had to come second to the story. And I know that there are many decent Conservative MPs who have gone on the record to say that the behaviour of the Prime Minister is indefensible. But equally, the behaviour of the Cabinet is craven.

Over the past few days, I have received scores of e-mails from constituents – some of whom have lost loved ones – deeply angered by the behaviour of Dominic Cummings, and the Prime Minister who rushed to his defence.

I have no way of knowing how this will unfold. Boris Johnson has an 80-seat majority. If he wants to he can probably brazen this out. But it brings the rule of law into disrepute. And, for me, it once again emphasises how important it is that we get to choose our own path as a country away from the toxic political culture embedded at Westminster.

John Nicolson is the MP for Ochil and South Perthshire