This is what happens when you put an arsonist in charge of a gas station. At some point he will strike a match, just to watch the whole place burn.

When Dominic Cummings appeared before a joint committee in the British Parliament this week to explain the government’s handling of the pandemic, there was never any doubt about the intentions of Boris Johnson’s former chief adviser. The man who has been described by Sir John Major, the former British prime minister, as a “political anarchist” was here to settle scores, ruin reputations, and bring the house down.

Liberated from the burden of collective responsibility and team loyalty that he had only lightly worn in 18 months on Downing Street before Mr. Johnson got rid of him, Mr. Cummings was not in the mood for moderation or explaining that things are difficult in a crisis. He wanted to spray blame, even if some splattered on himself. This was parliamentary scrutiny directed by Sam Peckinpah.

In a hearing that lasted for seven hours, the committee was told in the starkest terms that “tens of thousands of people died who did not need to die,” that the prime minister was “fundamentally unfit for the job” and prone to veering out of control like a shopping cart, and that key decisions had been delayed because of people going on skiing holidays and Mr. Johnson’s 33-year-old girlfriend, Carrie Symonds, being upset that someone had briefed the papers against her dog. The whole system, Mr. Cummings added, was “like wading through treacle.”

This was parliamentary scrutiny directed by Sam Peckinpah.

Matt Hancock came in for particular scorn. Mr. Cummings suggested that the health secretary should have been fired on at least 15 occasions, that he was a serial liar, responsible for “criminal, disgraceful behavior,” and should be blamed directly for not procuring enough protective equipment and not testing elderly hospital patients for the coronavirus before returning them to their care homes. Mr. Hancock will be able to make his rebuttal before the committee in a fortnight.

Some of it seemed farcical. Mr. Johnson so underestimated the pandemic, Mr. Cummings said, that he suggested a doctor inject him with the coronavirus on live television so that everyone would see that it was nothing to be frightened of. Hindsight is, of course, always twenty-twenty. The prime minister was of such little use, he added, that officials thought it best to keep him out of Cobra, the British equivalent of the White House’s Situation Room.

British health minister Matt Hancock was accused by Boris Johnson’s former aide of “criminal, disgraceful behavior” in his handling of coronavirus testing.

In one of the most ear-grabbing moments, Mr. Cummings described how in mid-March 2020, Helen MacNamara, the deputy Cabinet secretary, had revealed how bad things were going to get. “We’re completely f***ed.” He compared another moment to Jeff Goldblum explaining about the arrival of aliens in the science-fiction film Independence Day. Meanwhile, Mr. Johnson was acting like the mayor in Jaws, anxious to keep the beaches open no matter how many died. (Mr. Johnson’s allies may reply that the mayor was still in office for Jaws 2.)

Key decisions had been delayed because of people going on skiing holidays and Mr. Johnson’s 33-year-old girlfriend, Carrie Symonds, being upset that someone had briefed the papers against her dog.

Mr. Cummings did not even spare himself. “It is completely crazy that I should have been in such a senior position,” he admitted. “And it is crackers that Boris Johnson was in there. The problem was lions led by donkeys.” He regretted that, in a row over lockdown, he had not “held a gun to [Mr. Johnson’s] head” and threatened to tell the public that his boss was making a terrible decision.

To think that Mr. Cummings once had such little respect for scrutiny that in 2019 he was found to be in contempt of Parliament for refusing to appear before M.P.’s and provide evidence when asked. Now here he was being grilled by two moderate Conservatives of the type he used to despise: Jeremy Hunt, the former foreign secretary who had stood against Mr. Johnson for the premiership, and Greg Clark, a pro-E.U. former business secretary whom Mr. Cummings had once threatened to have “purged.”

All was forgiven since they served his purpose for revenge. Likewise, many political enthusiasts who once regarded Mr. Cummings as the Devil incarnate because of Brexit, a fork-tongued snake whose words were not to be trusted, were so delighted by his criticism of Mr. Johnson that they were tweeting his every word as if it were gospel. In politics, my enemy’s enemy is always my friend.

Patrick Kidd is editor of the Diary column in The Times of London