None of the revelations about the July 7 bombings should come as a surprise. British Islamist terrorists are a band of fanatics who are often known to one another and have sometimes trained or been indoctrinated together.

Some are skilled in anti-surveillance techniques, and their numbers are such that it is impossible for counter-terrorist agencies to keep track of them all.

If this causes shock, that is because there is a lack of understanding in Britain of the nature and scale of the terrorist threat.

That absence is caused largely because discussion of terrorism – whether conducted in the media or the mosque, the Commons or the courts – is characterised by complacency, stymied by denial or cloaked in secrecy.

Men such as Mohammed Sidique Khan and Omar Khyam were part of a network of Islamists who carried their religious radicalism into terrorism. Trace back their movements, their phone calls and their associates and you will link them all. The network that they were part of is still best called by the name al-Qaeda.

The tightly controlled al-Qaeda structure that existed before 9/11 was damaged by the US-led invasion of Afghanistan. But al-Qaeda has rebuilt itself in the tribal areas of Pakistan, spread its organisation to Iraq and is not in the state of disarray that many agencies claimed a year or two ago.

The head of Scotland Yard’s Counter-Terrorism Command said only last week that “the hand of core al-Qaeda” had guided a series of terrorist plots against Britain. Deputy Assistant Commissioner Peter Clarke spoke of “networks within networks, connections within connections, and links between individuals that cross local, national and international boundaries”.

A common pattern of movements exists in 7/7 and the fertiliser bomb plot. The terrorists travelled to and from Pakistan, where they met and were trained by al-Qaeda leaders. It has proved relatively easy for terrorists and jihadis to blend in with the 400,000 people who visit Pakistan from Britain every year and stay, on average, for 41 days.

Pakistan might be likened to the Irish Republic at the height of the IRA campaign – providing a relatively, if not entirely, safe haven for terrorist activity. And, as with the IRA, there is a sizeable population within the UK that feels beleaguered, persecuted and more hostile to the forces of law and order than it is to the terrorists.

Among them are active al-Qaeda supporters. Once they were visible at the Finsbury Park mosque or the al-Muhajiroun movement. Some figureheads are in exile or in jail, but their successors are busy raising money, indoctrinating and talent-spotting the best (or the most gullible).

Two thousand people are estimated to be involved in al-Qaeda activity in Britain. Khan had connections and associations dating back at least to 1999 (long before 9/11 or the invasion of Iraq).

There is no doubt that mistakes were made by MI5 and others, which allowed him to remain free to commit the outrages of 7/7. Equally, there is little doubt that, despite greater resources and tougher legislation, another bomber will slip through the net. Al-Qaeda will strike again.

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