We all know -- in principle -- that we are fed a great deal of spin by politicians and their 'political advisors', but we are seldom discriminating enough to sift through it all and determine what are the real reasons are for the messages we receive.

For example, most of the public are only just realising that the Iraq invasion was nothing to do with Saddam Hussein's 'evil' regime and his WMDs but the truly nasty medieval regime in Saudi Arabia which was (and still is) on a knife edge of survival. The inevitable insurrection or revolution there (the danger of which was intimated by the fact that the terrorists of 9/11 were mostly Saudi Arabians), whether by a few fanatics inflamed by Wahabbi clerics or by a more general uprising by the very large fraction of unemployed young males -- and probably aided and abetted by frustrated intellectuals, business classes and wannabe professionals -- could at least disrupt, and perhaps stop, the oil exports on which America crucially depends. Without the 20% contribution of oil from Saudi Arabia, America would immediately descend into an economic recession far deeper than that of the Great Depression of the 1920/30s.

But within the general spin justifying the invasion of Iraq, there was another spin, and it's probably going to take a very great deal longer before people realise its true significance. Probably, the truth will not be realised and accepted for two, three or more generations when historians can look back and have a more bird's eye view of the turmoil and confusion around us at present.

I'll grant that the politicians are, quite rightly, drawing attention to the threats of terrorism to modern, highly interconnected advanced societies, but when they talk about Weapons of MASS Destruction, what they really mean are Weapons of PRECISE Destruction. It is not the delivery of nuclear, and biological weapons that's the real problem these days (both of which require a huge and expensive infrastructure and subsequent detailed planning), it is that there are weapons of great destructiveness which are portable, easily able to be smuggled into countries and placed at the very centre of government.

In England, the government was almost destroyed twice in the last 20 years by WPDs. In 1984, the Provisional Irish Republican Army exploded a gelignite bomb in the Central Hotel at Brighton, brought the centre of the building down, and killed five close associates (and injured over 30 more) of Prime Minister Margaret Thatcher attending the Conservative Party Conference. She and most of the rest of her Cabinet were just yards away from the destruction. In 1991, the IRA tried to kill Prime Minister John Major and members of his Cabinet meeting in 10 Downing Street by lobbing three mortar bombs from a van parked around the corner. One landed in the back garden of No 10, only 40ft from the building. It made a crater several feet wide and shattered the upper windows. Major's Cabinet felt the blast as they were talking.

Neither of these really helped the cause of the IRA. It was only when the IRA bombed the Baltic Exchange in London in 1992 causing damage of £1 billion that meaningful discussions started taking place between the Northern Ireland nationalists and the British Government. The latter knew that if only one or two more bombings of important buildings in the heart of London's financial district would cause hundreds of foreign firms and banks to scurry out of the country and London would no longer be the second-most powerful (and profitable) financial centre in the world. At a later stage, during Northern Ireland talks in 1996, when the British Government were again stalling and foolishly locked out the Sinn Fein (the IRA's political wing), the IRA promptly bombed the large Armitage shopping mall in Manchester causing another £1 billion of damage and once again causing many foreign firms to wonder whether itis safe to invest here.

I'm sure that Osama bin Laden took note of all this, and this is why he decided to attack the Trade Centre buildings in New York rather than the White House. The twin towers were not chosen for "symbolic" reasons; he very probably thought that he could inflict immense devastation at the very heart of America's finance and international trade. He was wrong, of course. Although the buildings were destroyed, business recovered astonishingly quickly (and, it might be mentioned, they recovered because most firms whose offices were destroyed had distributed data systems -- more of that a little later).

Nevertheless, the cat was out of the bag. If the New York Trade Center was not quite the critical asset that Bin Laden originally thought, there are many others -- as revealed in the American media in the days and weeks afterwards. For example, there's a very large oil refinery on the east coast of America (I've forgotten where precisely) which, if I remember rightly, supplies one third of teh whole of America's petroleum products. This and many other highly concentrated locations of vital services and products are characteristic of our type of industrial society. The electricity blackout that occurred yesterday on the eastern seaboard of America is thought to have been caused by an accident or fault at one precise point in the whole system. Someone with a detailed knowledge of the three or four electricity grids that cover the whole of America could, with a similar number of well-placed bombs, bring the whole of the country to a state of complete helplessness.

The vulnerability of centralised nation-states and the nexus-critical characteristics of our types of developed economies can only increase in the coming years -- at least until the fossil fuel basis of our industrial and mechanical systems decline and some sort of decentralised electricity generation and manufacturing systems can develop. At the same time, the population of the world is destined to grow from just over 6 billion people at present to over 9 billion. The number of people who, rightly or wrongly, will have a burning sense of injustice, exploitation and persecution from their trteatment by the aflluent world is likely to grow well beyond the present relatively low numbers of Middle East fundamentalist Muslims. How many more terrorist groups similar to Al Qaeda will form in the coming years? Many, I would guess.

Nation-states can live with WMDs, difficult and tense though teh situation may be at times -- as America and Soviet Russia experienced it for 50 years during the cold war stand-off -- but can they live with WPDs? I wouldn't bet on it. I think that, during the next few decades, WPDs will prove to be one of that succession of innovatory weapons which ended specific types of governance and forced another, quite new, structure to come into existence. I think the WPD will prove to be quite as destructive to the modern nation-state as the Assyrian war chariot was to the several adjacent civilisations of the Middle East at around 500BC, or as the medieval cannon was to the castle-fortified feudal-state in the 15th century. WPDs will force a quite new type of governance upon us.