Primus inter pares. As a Latin scholar, Boris Johnson will be familiar with that phrase. It means “first among equals”, the traditional description of the constitutional place of the prime minister. Boris gave it a new twist more appropriate to the times: “et de omnibus mihi”. It's all about me.

He tried to justify his dogged refusal to resign on the grounds that he had a “mandate” from 14 million voters in the 2019 General Election. It is understandable that he thought that. In many ways he is right: he is probably the only politician in the Tory party who could have won that election based as it was on the mono-policy “Get Brexit Done”.

But that's not how our constitution works, as every modern studies student knows perfectly well. Walter Bagehot spelt it out in “The English Constitution” in 1867. (Scotland is different, but let's not go there) The UK does not have a presidential system of government, much as it may appear so – especially from the point of view of Number Ten.

Some academics have argued over the years that the British prime minister is no longer among equals but has evolved into a kind of president with a personal mandate. We have Boris Johnson to thank for demonstrating finally that this is not the case. A prime minister cannot assume the role of head of state or even head of the executive branch of government. He can try to pull the levers of government, but they just don't work. He needs a functioning cabinet to operate and the cabinet is still under the control of the party.

In America, Donald Trump could run his government without the Republican Party. He appoints all the offices of state rather like a temporary monarch, which in a sense is what the US President is. He eventually had to be forced from office by an election, which he contested till the end.

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There was speculation that Boris Johnson might have called a general election, to pull the temple down around his party's ears. Since the abolition of the Fixed Term Parliament Act prime ministers again have the power to decide the timing of General Elections. But again, he may have tried to do that and would have found that the levers don't work in our system.

The Prime Minister is a creature of party government and eventually, that reality dawned on him. He should have realised this much earlier than he did. his attempt to cling on long after the 'men in grey suits” as they used to be called had told him that his time was up had done him no favours.

Had he gone with good grace, he might have become a figure of some respect. A bit of a national treasure, even, able to laugh off misfortune and give a good account of his time in office. And there is much to be proud about.

He got Brexit done, he created the vaccine task force, he made the right calls on Ukraine and made Britain great again – at least in the eyes of Volodymyr Zelenskyy. But that will now be forgotten because of his arrogant and deluded attempt to defy the constitution and remain in office. A deluded vain and selfish individual who put himself above his country.