Westminster Tube Station/photo - forum.skyscraperpage.com

The journey up through Westminster tube station is my favourite in London. I've written that before here on openDemocracy, but the power of the architecture touches me every time. What also moves me, in a less thrilling way, is the decoration welcoming commuters emerging from central London's deepest hole. The station's magnificent concourse is invariably festooned with union flags.

For some reason, we still think the symbol of history's most aggressive empire is an appropriate image in the modern era. When I see its dripping red, I can't help but think of the metaphor often used to describe it by the victims of those who have carried it: the butcher's apron. I must confess I find it increasingly repellant.

And it's not just the flag. It's also what it has come to symbolise. When I arrived at the top of the escalators this time, the usual red, white and blue BAE Systems posters promoting machines of murder were complimented by a scattering of smaller union flags. On closer inspection, they were advertisements for a third runway at Heathrow – a construction which, if built, will help ensure any children I may one day have are deprived of the stable climate they deserve.

Sometimes, despite the fact that they exist to normalise a set of actions whose inevitable conclusion is death and destruction on a vast scale, I find myself shutting out the images we are forever surrounded with. But the beauty of the journey through London's commuter cathedral invariably leaves my emotions exposed, and my protections against brutal images are always down when I get to the top, and come across the most consistent gallery of British imperial imagery.

Out of the station and into a wet evening, I turned right, leaving Big Ben behind me. Heading round, past Westminster Palace I crossed at the green man, and made my way along the side of the fence currently penning in Parliament Square. Along that edge, facing Parliament, were a string of flags. Almost all had that same, blood-red, white and blue double cross in one corner, but were otherwise distinct and, to me, unfamiliar. A friend later wondered if they were the flags of the British Overseas Territories, and, counting 14 of them, and spotting the fluttering emblems of the Crown Protectorates on the other corner of the square, I concluded that he must be right. I suppose it's a good thing that our MPs are daily reminded that the sun still doesn't and hasn't set on the British Empire.

Here's the point. Symbols matter. It's why advertising firms and PR companies spend so much time and so many millions on developing them. Icons and images tell us stories about who we are. They confirm to us what is normal and what is abnormal. This is what propaganda is about.

As I've written here before, the symbols around Parliament are always fascinating because they are ultimately signs of weakness. The fact that MPs need to be reminded about what remains of the largest empire in human history shows how minute these remnants now are. The fact that Heathrow feels the need to advertise on what must be the most expensive ticket barrier poster-slots in the UK shows that they aren't confident of securing their runway – activists have seen them off before, after all. Perhaps most importantly, the need to cover everything you want MPs to see in a union flag tells us something profound about the contemporary crisis of British nationalism.

And because imagery matters, because symbols are much more than symbolic, the fact that the Occupy Democracy protesters I was headed to see had been forced off Parliament Square is more than frustrating for them. It is about much more than the usual crack down on dissent. It's about the power held over our imaginations by the imagery of power. The government doesn't want photographs of their parliament with protesters sleeping outside it because that's a challenge to their iconography, a disruption of the monopoly they have on what we imagine democracy to mean. They require any sign of the state to be a constant reminder of conformity, not a symbol of our right to resist.

But like the Heathrow posters, like the BAE advertisements, like the flags of the Overseas Territories and Crown Protectorates, ultimately, the exclusion of protesters from Parliament Square is a sign of a state with no confidence in itself. If the government felt that it represented the sovereign will of the people, it would have no problem with a relatively small crowd demanding changes. A country certain that it speaks for its people smiles calmly on dissent.

But then, we didn't need to see young people dragged violently out of Parliament Square by the police, we didn't need to see pizza boxes being confiscated from protesters lest they hold off some rain, we didn't need to see a peer arrested for complaining, in order to notice the lack of confidence at the core of the state which once ran a third of the world. Deep in the bowels of Westminster, there's a nagging worry that maybe, just maybe, the future belongs not to their besuited interns, but to their former classmates on the other side of a line of riot cops.

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The following evening – this evening - I returned to Parliament. This time, not in my previous holey jumper and jeans, but in my best suit and tie. Symbols matter. In Committee Room 16, we discussed the need for a written constitution in the UK, a codification of the powers of the powerful.

If anything tells you of the importance of such a document, it is the fact that MPs are permitted to ban protest within sight of their offices. That, and the fact that, in the worst run economy in Europe, those proposing the sensible and often moderate ideas which allow our neighbours to be more prosperous and equal than us are not inside the Palace of Westminster. They are outside, being beaten up by the police.