Boris Johnson did not need to pick today’s fight with his mercurial former advisor.

He is at least 10 points ahead of Labour in the polls, likely to score successes in the May elections and for once there is no pressing crisis at the top of his government’s agenda.

That was before the prime minister himself picked up the phone to newspaper editors on Thursday to blame Dominic Cummings for leaking against him, thrusting back in the spotlight his former right-hand man who disappeared from Number 10 holding a cardboard box five months ago.

Having relied on him through some of the toughest political scrapes of modern times, he will have understood the all-consuming nature of Mr Cummings’ hatreds and should have guessed he was picking on a man with nothing to lose and little respect for his former boss.

Predictably then tonight Mr Cummings, who performatively namedrops the Art of War, has retaliated.

In a 1,000 word blog released early evening, he accused the PM of planning to break the law, interfering with independent inquiries and employing a leaker as a close aide.

“It is sad to see the PM and his office fall so far below the standards of competence and integrity the country deserves,” Mr Cummings concluded.

But the danger comes from the specific allegations he levels.

Perhaps the most serious was over the PM’s plans to have “donors secretly pay for the renovation (of his and Carrie Symonds’ flat over Number 11 Downing Street) which were unethical, foolish, possibly illegal and almost certainly broke the rules on proper disclosure of political donations if conducted in the way he intended”.

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The allegation arrived on the day the government was attempting to sweep the renovation – which Tatler reported was because his fiance wanted to get rid of the “John Lewis nightmare” left by Theresa May – under the carpet.

A statement announced Mr Johnson had personally paid the likely £60,000 cost for the renovation bill which he previously wanted to be footed by donors.

The Electoral Commission does not yet appear satisfied.

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They told Sky News that they are still having “discussions” with the Tory party over whether undeclared donations were used at one stage to pay the bills.

The other serious allegation is about his deputy chief of staff Henry Newman.

Mr Cummings says he was identified as responsible for the leak of England’s second lockdown in the Autumn.

Mr Johnson baulked since Mr Newman is close to his fiancee.

The PM and his fiancée, Carrie Symonds, are said to have carried out a lavish overhaul of the flat above 11 Downing Street.

“I told him that he could not possibly cancel an inquiry about a leak that affected millions of people, just because it might implicate his girlfriend’s friends.”

Tonight Number 10 has not officially denied the allegations about Mr Newman, nor that the PM considered shutting down the inquiry.

A government source quoted disputes the allegation about Mr Newman, but similar government source quotes have proved inaccurate in recent days and so Number 10 must work harder to shut down this claim.

Mr Cummings has now said he wants to appear again before MPs next month, so there is more to come.

Plenty of MPs will be wondering whether Mr Johnson was wise to pick this week’s fight.

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