EIGHTEEN minutes separated the two airlines which were flown like missiles into the World Trade Centre - long enough for the world's media to point their lenses in the right direction for maximum effect.

Devastating in its execution, apocalyptic in its impact, it must have even surprised the terrorists who plotted the heinous act.

In terms of effective terrorism, it is going to take some topping and any future atrocities will undoubtedly take this into account.

It also has a bearing on whether the North of England really is a credible target. On the one hand, it could be. There is certainly plenty to have a go at. Menwith Hill listening station, near Harrogate, is manned by US personnel and is inextricably linked with George W Bush's $40bn Son of Star Wars missile defence system. So is Fylingdales early warning base, just a stone's throw away, on the North York Moors.

RAF Dishforth, beside the A1 in North Yorkshire, will be the first base in Britain to receive the Apache helicopter, the deadly American tank-buster which rained fire and death upon the retreating Iraqi army in 1991. Just down that very same road lies RAF Leeming, one of only a handful of front-line fighter bases in the country. And across the four lanes of the Great North Road lies the world's largest British military installation, Catterick Garrison.

"If they can hit the Pentagon, they can certainly hit any target they want," said Professor Pandeli Glavanis, deputy dean of the faculty of social sciences at Northumbria University. "The terrorists are very sophisticated - we are not dealing with kids - they have the knowledge, the experience and the resources."

The target this time was New York, but the fight is with the Western world and the sights could have been trained on any European country, any symbol of Western power, anything valuable to the infidels.

"Any area with a large number of military installations has to be a potential target," said Prof Glavanis. "They can hit anything they want to at any time."

But would they really want to attack "hard" targets in remote parts of the North of England? David Campbell, professor of international politics at Newcastle University, thinks not. "This was terrorism directed against symbolic targets," he said.

"Attacking a remote base is not sexy enough. It is going to be things that are more prominent, central, financially-related and easier to attack - Canary Wharf, the BT Tower, Lloyds - not the military.

"Ironically, New York also shows the absolute futility of the missile defence system - but perversely it will lead to more investment in it."

The tragedy in America is also expected to lead to calls for identity cards in Britain. Unlike most of continental Europe, Britain has no national ID card system which, in theory, would offer a quick and easy way to make sure people really are who they say they are