September 11, the eighth anniversary of which falls this week, ignited violent extremism across the world. The magnitude and savagery of the attack announced the arrival of al-Qaeda on the global stage — a terrorist group with the desire and capacity to mount indiscriminate suicide attacks causing mass loss of life.

Between 2003 and 2006, not a year passed without the United Kingdom being the target of a serious al-Qaeda-directed plot. Since the foiling of the airline plot in August 2006, however, there has been a period of relative respite. The attacks we have seen, such as at Glasgow airport, have been the work of lone or isolated operatives.

In addition, because the UK threat level has been reduced recently from severe to critical, some commentators are arguing that the worst is over. That is a theory I cannot buy into.

In assessing the threat from terrorism, the authorities will focus on what drives people into terrorist activity, the means by which they intend to express their beliefs and their capability to mount an attack.

The task of determining a threat level on the basis of the current intelligence picture is a world away from gauging if it is safe for the country to let its guard down. The consequences of confusing the two issues could be calamitous.

The martyrdom videos of the 7/7 bombers and those of the men convicted of the airline plot offer a graphic insight into the hatred towards non-Muslims. There are common traits to each UK plot suggesting that it is highly likely that when these individuals left Britain for jihad in Pakistan they were on the way to radicalisation.

For these men, Pakistan was a terrorist finishing school where they met veteran al-Qaeda fighters and leaders. In a short time their views would have hardened. Their contact with these people was maintained on their return to Britain.

Recent events in Pakistan appear to have disrupted the way that al-Qaeda operates in terms of the threat to Britain. The intelligence assessment is that Rashid Rauf, the British fixer, and Abu Obaidah al-Masri, the master bombmaker, are dead. Their deaths, and the imprisonment in Guantánamo Bay of Abd al Hadi al-Iraqi, removed influential leaders and impaired the organisation’s ability to direct attacks and recruit suicide bombers.

Meanwhile, al-Qaeda’s militant allies are focused more on taking over the country rather than planning attacks on the West.

None of these facts, however, can halt the promotion of extremist views or the undiscovered terror cell devising new plots.

There are some parallels to be drawn from the serious crime arena. If gang leaders are taken out of circulation, the group can become dormant. It is either replaced by another gang, develops alliances or falls back and regroups.

But the threat will persist. The gang will be resurgent because the criminal mindset is driven to make money. Similarly, the terrorist remains driven by extremist beliefs. After a setback both will strive for renewed leadership and capability.

There are indications that perhaps al-Qaeda is evolving in a similar way. If the leadership has been disrupted and Pakistan is becoming more difficult to operate from, it will seek a new nerve centre. There are real concerns that Somalia is becoming a more significant location. The 21/7 bombers hailed from the Horn of Africa and the suspected Melbourne military camp plot involved individuals from Somalia.

In Britain, the Somali community feels alienated and distrustful of the authorities. To some extent this mirrors the sense of detachment reflected in other Muslim communities across Britain in the aftermath of September 11.

The threat level has been reduced because known intelligence is telling the authorities that al-Qaeda is not as potent as it was a few years ago. But that should be seen as a short-term position. This is a lull in hostilities, not a cessation.

Andy Hayman was Assistant Commissioner for Specialist Operations at Scotland Yard 2005-08

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