I have no linear memory of what I was doing on this day ten Septembers ago. It's more a loose thread of incidents that unspools whenever I remember Sept 11 .

I remember being in my office, which I shared with a few others, looking at huge plasma screens displaying performance statistics, flicking between those and my own computer. Then the office door was flung open. And the day began. That day.

Whoever it was, burst out that a plane had slammed in to the Wall Trade Centre. After that my sense of chronology goes. Someone brought up the BBC on one of the plasmas that I remember, as I do more and more people crowding into the office, silent, awestruck, barely talking, barely comprehending.

I remember vividly telling someone that at least 50,000 people worked in the WTC complex. I knew that from numerous visits to New York and the simple fact of spending time in it's subterranean shopping complex, where I could go to either wait for a friend who worked on nearby Hudson Street, or to wander around the two storey bookshop (Barnes and Noble ? Borders?), and for this more prosaic reason, that was where one of the very few free public toilets in Lower Manhattan was.

I remember seeing each of the Towers waver, then fall. I've no idea of my inner emotional state, horror, shock, disbelief, certainly disbelief; there was something about that rolling, broiling cloud of dust that defied understanding. That was a trope of science fiction, except it was n't, it was fact, and within that whirlwind of dust and ash, people were dying.

Even now, ten long years on, I still wonder whether it was a film. It's the unreality of being witness to something so extraordinary, so terrible. It's the province of films, but it was n't, it actually happened. Three thousand miles away from London's sister state, I saw with dozens of others crowded into a small office, as did millions worldwide, people die. I still can't believe it.

I remember eventually leaving work sometime in the evening and into a shell-shocked London. Past a winebar on Walbrook that always heaved with noise and laughter, that this evening was overflowing with hundreds of subdued office workers simply watching television, just the occasional murmur of a voice.

I remember the anxiety of trying to reach my friend, an old girlfriend in fact, who worked on Hudson Street. Endless e-mails then the utter relief of getting a line from here; shocked, fearful, but safe.

I remember an e-mail from a cousin working in Canary Wharf, apprehensive that they were a target and that an airliner had been hijacked in the Netherlands and was headed there.

That's all I remember, perhaps I could squeeze more out if I tried, but I can't, this is really all I remember of a day I wish had been as anonymous as all those that preceded it.