LIKE many people, I have a certain fascination with old technology. Take grandfather clocks and steam trains for instance. We do not need these things anymore. Digital clocks and diesel-electric trains have rendered them obsolete. But still there is something mesmerising and enchanting about them. All those tiny brass wheels, tick-tocking their precision-engineered path through time. The furious movement of rods and pistons, the roar of the firebox and the hot angry hiss of escaping steam. They speak of something great and noble: human skill and knowledge harnessing and taming wild nature through the application of mechanisms.

Mechanisms made the modern world. John Harrison’s chronometer – invented in 1761 – marked a major technological advance. In keeping accurate time at sea, it became possible to calculate longitude, and thereby for a ship to be able to pinpoint its position on the globe, revolutionising global trade. Thirty-nine years later, in 1804, Richard Trevithick’s steam locomotive inaugurated the railway age by carrying 10 tons of iron at the break-neck speed of five miles an hour.

The Constitution of the United States was ratified in 1788, right in the middle of that mechanical transformation. It reflects the same spirit: a belief that the raw nature of political power, generated by the people themselves, can be harnessed and tamed by ingenious mechanisms.

The Founding Fathers who wrote the US Constitution were cunning artificers of the republic, engineers of a political order in which power would run according to known and stated rules.

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Any revolutionary can mix the right elements together and create an explosion – which usually results only in lots of dead bodies. It takes a constitutionalist to channel that outburst of power into good governance through stable and effective democratic institutions.

The US Constitution is indeed an obsolete machine. No-one creating a constitution today would take the US Constitution as their model. Constitutional technology has moved on and there are plenty of better designs available.

We could have a mid-20th-century diesel-electric constitution, unlovely but reliable, like those of the Commonwealth Caribbean. We could have a sleek modern superfast bullet-train constitution, like those of Sweden or Latvia. But that is another story. The remarkable thing about the US Constitution is not how badly or inefficiently it works, but the fact that for such a primitive and clunky design it works at all.

There was lots of hot angry steam hissing around the Capitol building last week, as violent mobs incited by the sitting president attempted to disrupt the recording of the Electoral College votes and the announcement of the official result of the 2020 presidential election.

It was a foolish move by a president who cannot admit he lost the election. For those around him, who have stood by him and supported him in every barefaced lie and egregious act so far, it provides a golden opportunity to recast themselves as good guys. Already scores of Republican senators, who did not vote for Trump’s impeachment last year, are lining up to denounce the violence. Vice-President Mike Pence, who broke with Trump at the last minute and decided in the end to do his constitutional duty, is being hastily rebranded as the hero of the hour.

Even so, the fact that Pence did do his constitutional duty is proof, once again, of  the value and importance of written constitutions.

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The US Constitution might be old and cumbersome, it might not by modern standards even be very democratic, but it is the only thing now holding that fractious, bitterly divided country together. When trust evaporates, when goodwill fails, when basic civility breaks down, nothing but adherence to the rules can get a country through.

The process of US presidential elections is absurd. No other country does it that way. But the rules were, in the end, followed. They were not followed simply because they exist as words on a page, but because of what those words represent: legitimacy. You only get to be president of the United States if you win in accordance with the rules. A mad mob armed with guns besieging the Capitol building, egged on by a president dangerously intent on destroying what he cannot keep, cannot obtain that legitimacy.

More constitutional rules might now come into play. There is serious talk of invoking the 25th Amendment, a procedure that allows the vice-president and Cabinet to strip the president of his powers if he is “unable to discharge the powers and duties of his office”. At this late stage in the Trump presidency, that would be a symbolic move. Whether it will happen remains to be seen.

Yet through all this difficulty, the rules matter. Trump governs under a constitution. He does not have the vast power that a British prime minister with a majority in the

House of Commons possesses, to change the rules as he goes along. The fundamental message of the US Constitution, more than 200 years on, is still clear: “Play by the rules, or pick up your Trump banner and go home.”

Childhood campaigner, Sue Palmer, is next week’s guest on the TNT show at 7pm on Wednesday.