I keep reading how the recent attacks in London and Glasgow failed. This strikes me as naive and narrow-minded thinking. The plots failed to kill anyone - that is true - but that was not their only purpose. Possibly not even their main purpose.
The point of terrorism is not simply to kill people. It is intended to create certain conditions through which a cause can be advanced. Death is merely a by-product.
The first intention of terrorism is to create a climate of fear, concern and insecurity. That is obvious. It is intended to "terrorise" the civilian population. The purpose of this is to make the civilian population doubt the ability of it's government to protect it. This is, of course, an irrational doubt because no government can ever protect it's people from indiscriminate acts of murder. However, what it does do is create the situation where the government are forced to be seen to act.
And this brings us to the second intention of terrorism. To cause disruption, inconvenience and cost. The government responds to an act of terrorism by embarking on a series of measures designed to demonstrate that they are acting. Hence we see long queues at airports, cars searched, people frisked, flights cancelled and armed police everywhere. All of this disruption and inconvenience is a direct result of last weekends attacks - and it cost millions of pounds of taxpayers money.
The third intention of terrorism is to cause a government to make concessions to a cause. The obvious example of that was in Madrid where a few murderous extremists were able to influence the outcome of an election. But it happens here as much as anywhere. In 1940 Churchill's response to the threat from Nazi Germany was "we shall defend our island, whatever the cost may be", but a prolonged campaign of terrorism by the IRA led the government of Britain to the position that it was preferable to have a "peace" whatever the cost may be. The cost of that decision - apart from the fact that former terrorists now sit in Parliament - is that terrorists the world over now believe that their tactics will force concessions eventually. Indeed, the Islamic terrorism of recent years has yielded concessions far more quickly than the IRA ever managed.
The next objective of terrorism is to divert resources. This is a particular objective of Islamic terrorism. The intention is to force the police to concentrate so much of their effort into coping with terrorism that they are unable to apply themselves to the other aspects of their job - preventing crime and disorder. This is essential to Islamic ambitions because a crime riddled society craves morality, order and discipline - and Islam ostensibly offers these (particularly in a nation where the traditional Christian morality, order and discipline has been significantly eroded). As crime thrives so does the people's desire for something to act as a bulwark against that, and Islam - and particularly fundamentalist Islam - appears to many as an attractive option. So more people become Muslim and more Muslims become fundamentalist.
I could go on, but then this post would last forever. I hope I've got the point across that terrorism can not be considered in such simple terms of success or failure based on the number killed. There are a multitude of objectives behind terrorism and, in this latest attack, they have largely succeeded and will continue to succeed until we finally understand what the real motivation is behind their campaign and start to deal with that.
And, in case you are still unsure of what motivates Islamic terrorism - it is the establishment of Islamic ideology as the dominant global political force, the eradication of western liberal democracy, the destruction of Israel and the subjugation of unbelievers.