Al-Qa'ida's attacks on London in the summer of 2005 exposed Britain's vulnerability to a new kind of terrorism.
The discovery that the July bombers and their accomplices were home-grown meant the police and the Security Service needed to rethink their counter-terrorism tactics. The subsequent hunt for groups of British-born men who might be planning similar attacks was given the highest priority.
Key to the new approach would be deeper penetration into Muslim communities. The police worked hard at gaining the confidence of Muslim leaders; the Security Service stepped up its recruitment of informants. The Government also played its part, bringing in tough anti-terror laws and funding programmes aimed at discouraging extremism in Muslim communities.
Ministers continued to justify the levels of intrusion and disruption to people's lives by claiming that Britain was under attack and faced a public emergency.
But the stakes have been raised so high that little notice has been taken of the damage done to Muslim communities by heavy-handed policing and intelligence gathering. There have been growing concerns that terror laws are being used by the police to victimise Asian communities, while The Independent has reported on complaints about MI5 harassment of individual Muslims as part of an informant recruitment programme.
In the past few days, official warning bells have started to sound over the dangers of continuing to enforce these measures without properly considering their impact.
Last week, Parliament's joint committee on human rights said that such a high threat level was not credible because it had been continuously maintained for such a long period of time. The MPs called for a review of all terror legislation passed since 11 September and asked whether it was realistic to say the state of emergency which existed at the time still remained now.
This week, another influential parliamentary committee concluded that the Government's central policy on countering extremism in the community had badly backfired. Many Muslims told the Communities and Local Government Committee that they believed the purpose of the Prevent programme was to "spy" on Asian communities, and that the Government was using funding to engineer a moderate form of acceptable Islam.
The MPs said ministers should investigate claims the strategy had been hijacked to gather intelligence on alleged radicals. Committee chairman Phyllis Starkey said Prevent had been "discredited" by the misuse of "intelligence gathering" which had "fed distrust".