I remember hearing a British raconteur telling a story a few years ago about a friend of his who had been late for work. I remember thinking it was a strange subject for a story.
It seems his friend had been given a bright green shirt as a birthday present by his mother. He had been too discreet to say that he did not like it. So he decided to visit the shop before work one day to see if he could exchange it. The shop assistant delayed him for about 15 minutes, as there was no receipt for the shirt. In the end, he was offered a different shirt and, realising he was late, set off running for work. He arrived 15 minutes late.
An unremarkable story? On a normal day, yes. But this was not any normal day - it was September 11, 2001. And the raconteur's friend worked in the World Trade Centre in New York. By the time he arrived, the North Tower had already been hit by the first plane. If he had been on time, he would have been on a higher floor than the plane hit.
His mother's poor taste had saved his life.
This story is just one of thousands about how close terror came to many people's lives that day. Of those who did not have near misses, there are many others who knew people who worked in the cities affected. And more still who thought they may be next.
What's the significance of this? It is that terrorism actually affects relatively few people directly, but many people indirectly. Figures given in Bjorn Lomborg's piece in this month's issue indicate that transnational terrorism has killed about 500 people a year since 2001. But this figure is dwarfed by those who have felt the fear these attacks were designed to create. This is the purpose of terror attacks - for each person killed, frighten thousands more.
In this issue, we look at how much it costs to tackle terrorism, its changing tactics, its ability to be both targeted and indiscriminate, its sources of support and how organisations like NATO can tackle it.
There is no easy answer. The odds are often with the terrorists. After bombing the Brighton hotel where Margaret Thatcher was staying in the 1980s, and failing to kill her, the IRA issued a statement. It read: 'Today you have been lucky. But you have to be lucky every time. We only have to be lucky once.'
Terrorism is a moving target. Security organisations need to move with it - or faster.