In answer to the obvious question, I was in double biology, cutting up potatoes for my GCSE coursework. There was a television in the school science labs, and in students rushed, in ones and twos and in hushed astonishment, as the twin towers burned and then fell. One boy rushed to call his father in New York. The normal hierarchies of age and status were suspended temporarily as sixth-form footballers and geeky kids in Year Ten shared a packet of biscuits someone had produced. We all munched away silently, watching the world change for ever.
Memory is a funny thing, particularly collective memory. Once or twice in a generation come events so seismically significant that they seem to resist analysis, and all we can do is remind each other what we were doing when we found out. The baby boomers remember where they were when Kennedy was shot; my parents remember where they were when the Berlin Wall fell; today, we remember where we were a decade ago when Islamist terrorists attacked the Pentagon and the World Trade Center. As the footage of human beings jumping to their deaths from the blazing towers rolled and re-rolled, a tacit understanding grew that to attach meaning or context to these attacks would be unthinkable, impossible.
Unfortunately, meaning and context were precisely what we were starved of over the next ten years, as western leaders appeared to deem this atrocity so numbing to debate that anything could be done in its name. Even language became warped in the wreckage of the towers: tens of thousands of Iraqi children became "collateral damage", outsourced torture became "extraordinary rendition", and the bombing of nation states became an amorphous war on "terror". The legitimate grief and shock of those who lived through the 2001 attacks were co-opted to sanction a decade of cruelty, misinformation and war, and, in the west, a generation grew up understanding that politicians cannot be trusted.
Even ten years on, we refer to the events of that day in superstitious shorthand. When we say 9/11, everyone knows that we don't mean the mediocre mid-1990s boy band. Fear of a name, as Dumbledore teaches us, increases fear of the thing itself, and fear is just what leaders on both sides of the war on terror were counting on.
There are some political realities so ponderous that only fiction can understand them. In Ken MacLeod's 2008 novel The Night Sessions, the race to stop a religious terrorist cell from blowing up two skyscrapers and killing millions is thwarted when it is discovered that everyone has been looking in the wrong place. Instead of the planned attack, the fundamentalists destroy a major piece of economic infrastructure, causing a global downturn.
Caught and interrogated, one terrorist coldly explains that even though no one has died, millions of lives will be shortened and made materially harder as a result of the coming recession - and hence the human cost of this piece of global sabotage will be far higher than any one dramatic act of mass murder.
The remarkable prescience of this chilling little book, published a month before the toppling of Lehman Brothers, has stayed with me since. Because it turns out, ten years after history appeared to be rewritten in plumes of smoke across the Manhattan skyline, that we have all been looking in the wrong place. It turns out that the grand story of the early part of the 21st century is not the clash of civilisations, of Islamist terrorism versus western democracy, but the struggle of the financial and political elite against their own people as the free market buckles under its own weight, a new bankruptcy hastened by two desert wars and years of cheap post-9/11 credit. The greatest threat to democracy is not external attack, but internal collapse.
Ten years after 9/11, the world has moved on. Realisation is dawning that the great danger to western democracy was never a shadowy super-villain skulking in the desert, but inequality, alienation and economic collapse. The main threat to our collective way of life is not sudden and brutal, but gradual and callous: it's the wearing away of everything that made ordinary life decent and bearable, the slow erosion of civil society into something mean and desperate. And that truth is far more terrifying than any dirty bomb.