In Whitehall and Westminster the situation resembles the early scene in The Wizard of Oz when Dorothy’s house lands on the Wicked Witch of the East, flattening her in the process. The nervous inhabitants of the village, eyes wide with wonder, emerge to discover that they are free. They celebrate the end of tyranny.

In Oz, there is a catch. The Wicked Witch of the West soon turns up promising revenge. In Borisland, there is no such complication. Not only was Lee Cain vaporised last week, but chief aide Dominic Cummings was taken out too, when Carrie Symonds and her gang landed.

The revelation by Francis Elliott in The Times last week that Cain was “poised” to be appointed chief of staff was, in terms of the power struggle for control of this government, the equivalent of a bomb going off. Carrie Symonds, the PM’s partner, thought Cain a disastrous choice. She and her allies moved to block the appointment, prompting Boris to change his mind.

What flipped Boris into firing Cain and Cummings when he had stood by the pair for the last year? It’s not as though it was going well before this. He repeatedly refused to fire them despite warnings from friends that their hyper-aggressive approach was at risk of destroying his reputation and his relationship with Tory MPs and more.

Friends and former colleagues explain that it comes down to him detesting bullying and the way he feels strangely protective towards the characters he picks up along the way.

“Boris hates bullying,” says one Borisite. “If he thinks the media are bullying someone then he digs in.”

This may be the case, but what his team were doing was in itself pretty menacing, surely? The sacking of Treasury adviser Sonia Khan – settled last week ahead of an employment tribunal – was hardly kind?

It seems that any concerns Boris felt were eclipsed by his belief that Cain and Cummings were central to his election victory and to getting Brexit done. He needed them, they told him, to guard against disloyal people who would give him bad advice and make him too “establishment”. Although their behaviour was at times very weird, that is not always a disadvantage in  Borisland. Boris can be weirdly attracted to damaged or eccentric individuals.

Plainly, Cummings should have been fired over the Barnard Castle business, because it eroded trust in the government by sending out a “one rule for them, another for the rest of us” message on lockdown.

Yet the media pile-on, with TV crews hunting him, a journalistic jamboree inspiring a blizzard of ghastliness on social media, only made Boris determined not to give in, not to feed the beast, not to submit to bullying.

What changed last week? What made him snap? Cain and Cummings were perceived by Boris to have been cruel about Carrie Symonds, via nicknames and tolerating laddish mockery among their associates. Regardless of their denials, that they should let this perception lodge itself in Boris’s brain turned out to be a fatal mistake. Whereas he once perceived Cummings and Cain to be loyalists being bullied, by last week the balance of power had changed. He didn’t like what they were about and he wanted them out.

Ultimately, Cain and Cummings had broken the “omertà” that exists around Boris. Want patronage or even tolerance by Boris? Get tangled up in criticising his private life or be at odds with those he is most attached to, and eventually he’ll flatten you.

The Hound is the new diary published by the Reaction team. If you would like to become a Reaction subscriber and receive editor Iain Martin’s newsletter on politics and much more, subscribe here.