By Andy Tighe
Home affairs correspondent, BBC News
The terrible events of 7/7 are often described as a wake-up call. Islamic suicide bombers had finally struck in the heart of Britain's capital.
But the bombings - in which 52 people were killed - came as no surprise to the government, police or intelligence services. For some time they had been predicting it was not a case of "if" but "when" the UK would suffer an attack.
Bombs on three Tube trains and a bus killed 52 people
Since hijacked planes crashed into the World Trade Center on 9/11, counterterrorism became a top priority. Spending doubled to more than £2bn a year. And new laws were drafted to meet the evolving threat.
But it was not until our TV screens showed the bleeding, terrified victims of 7/7 emerging from smoke-filled Underground stations that many people appreciated just how vulnerable they had become.
But questions were soon raised about whether the authorities could have done more to prevent the attacks; about whether intelligence was properly shared and acted upon.
While an independent report laid no blame, measures were soon taken to strengthen Britain's counterterrorism capability.
The domestic security service MI5 stepped - partially - from the shadows, with a recruitment drive, a more informative website and new offices in the north of England.
The police, too, were reorganised with new counterterrorist units set up outside London.
More controversially, the government passed a series of new laws, and battled to extend the period of pre-charge detention for terror suspects.
After a drawn-out parliamentary wrangle it settled at 28 days, though there are indications that further changes could be on the way.
What did all this achieve? The authorities point to a series of successful convictions, including the jailing of Dhiren Barot, a senior al-Qaeda figure who plotted bombings in London and America.
But there have been setbacks. The system of control orders - to deal with terror suspects who have not been put on trial - has been widely criticised, with a number of individuals absconding.
Muslim leaders have complained about the large number of young Asian men arrested under anti-terrorist laws but later released without charge.
One man has been charged over the suspected attack in Glasgow
And while the police and MI5 have managed to accumulate an unprecedented database of terrorist suspects, they cannot be sure that every dangerous individual is on their books.
The threat is constantly evolving. The attacks in London and Glasgow at the weekend were foiled not by intelligence-led operations but by a combination of sheer luck and the bravery of a few individuals.
After 7/7, some senior security officials felt that many people did not fully appreciate that it signalled the beginning of a new phase of extremist activity, that further attacks were not only possible but likely.
With fresh horrors now on our screens, one of the police officers leading the current investigation told me a few days ago: "If this isn't a wake-up call, I don't know what is."