If you hear on the radio that an "intelligence-led" operation had resulted in arrests, you might feel reassured. Yet the invasion of Iraq, the shooting of Jean Charles De Menezes and the storming of a house in Forest Gate in London last August were all "intelligence-led".
The quality and sources of intelligence became a critical issue during my examination of the fate of the Belmarsh 12 for Dispatches. These were terror suspects rounded up after 9/11, who could not be deported because their country of origin practised torture. They were presented as Bin Laden's "terrorist cell" in Britain - the public symbol of Britain's counter-terrorism strategy, as well as the central characters in a mammoth legal drama surrounding the government's right to detain suspects indefinitely without trial.
The House of Lords eventually declared their detention a breach of the European Convention on Human Rights. They have never been before a jury nor heard the evidence against them. Now they are being sent to their homeland or placed under house arrest.
While the men were accused of ties to al-Qaeda, they were also linked to the GIA, the murderous organisation that wrought havoc in Algeria in the 1990s. Nine of the Belmarsh 12 are believed to be of North African origin, but even those from elsewhere were accused of involvement in the GIA. Algerians were also implicated in "terror plots" in 2002 that never materialised, involving poison gas on the underground, a ricin factory in London and attempts to attack a "high-profile target" in Edinburgh.
Now information is emerging that the GIA was in fact a construct of the Algerian regime, in particular of its intelligence agency, the DRS. A growing number of former army officers, diplomats and spies accuse the regime of complicity in the murder and disappearance of tens of thousands of Algerian citizens in the 1990s: 250,000 died during that bloody decade but no one from Algeria is being charged with war crimes.
No international body and no foreign journalists have been allowed access to find out what really happened. And, because Algeria's military rulers have become their close ally in the "war on terror", western governments are not asking awkward questions.
Mohamed Samraoui is a dapper man in his fifties, living in hiding in Europe. He spent 22 years in the DRS and says he left after refusing to murder a prominent Algerian dissident in Germany in 1996. The former spy told me that five days after 9/11, Britain was handed a dossier naming 1,800 "terror suspects" from North Africa living in the west.
Were these men a threat to Britain? He laughs. "The names on that list were not wanted terrorists. They were opponents of the regime who had sought asylum in the west." MI5 was "naive and stupid" to swallow information from their Algerian counterparts, he added. The dossier was handed over so that the generals, who hold the reins of power, are not held to account for the massacres they ordered in the 1990s.
No wonder the government is increasing the remit of secret hearings. When intelligence is turned into evidence and brought before a jury, 12 good men might be swayed by witnesses such as the Colonel Samraoui.
Phil Rees's report "Dispatches: at home with the terror suspects" is on Channel 4 on 5 February, 8pm