I REMEMBER standing at the top of the World Trade Centre four years ago. It was astonishing. At 1,368ft up and 110 storeys high, it felt like the top of the world. Everything below - the whole of the great city of New York - looked so small.

It was a fantastic piece of architecture and, as I stood there, I remember wondering how on earth they had managed to build something so tall, something so vast, in such a crowded corner of the planet.

When I turned from the north tower and looked across to the south one, only then did I realise the immense scale of the buildings. On television in the last couple of days, the towers have looked so slim and slender. But, when you are there, you see how big and broad they really are. So, as much as anyone, I was stunned to see these constructions crumble following Tuesday's terrorist attack.

I visited New York three times in 1997 when I was researching crime reduction strategies, and it is like nowhere else on earth. The first time I flew into Manhattan, I remember looking out of my plane window and seeing the geometric skyscrapers spread out beneath me. It looked like a city made out of cardboard boxes. But on the ground, it reminded me of Gotham City in the Batman movies: so tall, so towering.

As my research progressed, I got the impression that it was a truly cosmopolitan, multi-cultural place. The city authorities had worked with the people to make it attractive to residents and tourists. A street near Broadway had been full of sex shops, but these had been replaced by up-market boutiques. Derelict buildings had been put to good use and a crime reduction strategy - what I was most interested in - had reduced the feel of fear on the streets.

Consequently, visitors had flocked in. As mankind makes the world smaller, travel is no longer thought of in terms of miles but in time. By plane, I can be in London in 45 minutes, Paris in an hour and a quarter, and New York in just seven hours. That is what has shocked me most about the week's events: they have been so close to home.

On Tuesday evening, I was talking to a friend from Stockton, Alison Crake, who was in a Manhattan hotel. She was telling me how she'd been watching on television the fire in the first tower when the pictures came on of a jet crashing into the second - and she heard and felt the explosion outside her window. This is how close this terrible crime against humanity is - someone I know has been personally caught up in it, has been personally covered in the dust of it.

And the fallout will affect us all. Our pensions and our mortgages are at the mercy of how the world markets react to having one of their own blown up before their eyes. Oil prices have already shot up; the world's airline schedules are in chaos with planes due to be in New York now grounded in Dubai or Australia.

Most of all, I fear the fallout of the American reaction. But on Tuesday night, I saw a new side of President George W Bush. When he spoke of this being a test of America's resolve, he was spot on.

The American people will be driving him towards vengeance, but I hope he can pass this test by not lashing out in a manner that, while playing well at home, could endanger us, his allies, from further fallout. Because we are closer to America than many of us realise.