LONDON is full of shit. It has been for a long time. With so many people crammed into a dense urban environment, it could hardly be otherwise.

Overflowing cesspits leaking into shallow wells made early Victorian London rife with cholera. Into this mire stepped the heroic Metropolitan Board of Works, which proceeded – after the Great Stink of 1858 – to construct a massive and marvellous sewage network.

Sewers and drains became part of imperial Britain’s self-image, celebrated even in its poetry. Rudyard Kipling, the arch-imperialist bard of the Raj, praised sewerage with the words, “I believe in well-flushed culverts. This is why the death-rate’s small”.

Sir John Betjeman’s In Westminster Abbey includes the line, “Think of what our nation stands for, […] democracy and proper drains.”

The connection between “democracy and proper drains” was not coincidental. Victorian sewage systems were not just a scientific and engineering triumph, but an institutional – even constitutional – achievement. Cholera was beaten by the ability of an increasingly capable state to harness and manage resources to meet public needs. It was the work of planners, officials – and ultimately parliamentarians.

The Metropolitan Board of Works owed its existence to an Act of Parliament, passed because the Government, depending on a majority in the House of Commons that was increasingly sensitive to public opinion, had to respond to public pressure.

During the period bracketed by the 1832 Reform Act and the 1911 Parliament Act, the institutions of Westminster Model democracy were first developed at home and then exported around the Empire. Much of this development was organic, hammered out in political compromises which later congealed into the conventions of the constitution. These unwritten but morally binding rules were the cement that held the British system together.

We are now in the midst of another public health crisis. The London sewerage system built by our Victorian ancestors is still going strong, but the cement of the Victorian constitution is full of dangerous cracks.

One such crack is the over-use of press conferences.

This week, for instance, the Prime Minister decided to announce changes to England’s Covid lockdown policy by means of a press conference.

This is unacceptable. It violates section 9.1 of the Ministerial Code. More than that, it breaches a key principle of the Westminster Model of parliamentary democracy: major policy statements should be made in Parliament, where they are subject to parliamentary debate and questioning.

For this, the Prime Minister was rightly rebuked by the Speaker, who has become increasingly heated in demanding that proper respect be paid by the Government to the House of Commons.

Parliament is admittedly a very imperfect institution. Only half of it is elected, and that by an electoral system that is grossly disproportional. Nevertheless, it is the one place where ministers can publicly be held to account and where Government policy can be scrutinised, questioned, debated, investigated.

A press conference, before invited tame journalists, offers none of that.

The Government’s excuse for the press conference was that it wanted to speak to “the people, not to Parliament”. That is insulting. It is populism at its very worst.

Democracy, properly understood, is not unlimited majority rule. It is a complex political system that combines representative and responsible government with civil liberties and the rule of law, checks and balances, impartial administration, decentralised authority, and means of participatory engagement in decision-making.

Populism is a grotesque caricature of democracy. Populists want to kick over the barriers that restrain abuses of power. Their attempts to weaken the judiciary, politicise the civil service, sideline parliamentary Opposition, infringe fundamental rights, centralise power, and restrict public participation by draconian anti-protest or voter-suppression law, must be therefore seen as attacks on democracy.

This is true even, or perhaps especially, when it is done in the name of “the people”.

This little crack might seem like a small thing fret about, but it is far from an isolated case. Since coming to power, the current UK Government has delivered blow after blow against our parliamentary democracy’s crumbling norms and conventions. It is only a matter of time before the whole thing comes crashing down.

The United Kingdom, where there are no constitutional safeguards, is terrifyingly vulnerable. It comes back to the same fundamental point: the unwritten constitution has outlived its usefulness. It may seem paradoxical, but the only way to preserve, restore and reanimate our system of parliamentary democracy is to write it down in a new constitution, where the ground-rules are agreed, clear, authoritative, and cannot be ignored by those in power.

Independence would provide an opportunity for such constitutional renewal. But do not think for a moment that Scottish drains unblock themselves or that Caledonian air will blow the stench away. Well-flushed constitutional culverts, that’s the thing to keep us out of the shit.

Laura Moodie of the Scottish Green party is the guest on the next TNT show at 7pm on Wednesday