US: Walking through the concrete canyons around Wall Street yesterday was like being a pedestrian in Belfast in the early 1970s: you knew there were people planning to set off car bombs and you just hoped that it would not be at that moment, in that place. Conor O'Cleary reports from New York.
You could see from the faces of traders, office workers and street vendors that the thought that it could happen again had been forced from the recesses of the mind (where it never leaves) to the forefront again.
We have got used to the police checkpoint at the corner of Broadway and Pine Street where vans and lorries are always pulled in for inspection.
We have lived for years with the ugly concrete barriers along the pavements - some have even been replaced by tasteful metal bollards.
We had got used to the police monitoring the hundreds of sightseers with backpacks who make the pilgrimage to Ground Zero every day.
But after the terror alert on Sunday we could see there was now much more police activity on the streets. Anti-terrorist officers in black metal helmets cradled automatic weapons outside financial buildings.
Police on motorcycles cruised around side streets, peering into parked cars, asking bakery and laundry truck drivers to rattle up their concertina doors so they could poke around inside.
Kids with backpacks were watched now as if they were potential suicide bombers. Even several blocks away there were police prowling around, as if anticipating that if the terrorists couldn't carry out their plans, then they would simply explode the devices at some other 'iconic target', as Homeland Security Secretary Tom Ridge now calls any big financial building.
New York police also closed several streets in midtown Manhattan and banned trucks from bridges and tunnels leading to Wall Street.
The new intelligence was apparently found on the computer of an allegedly high-ranking al-Qaeda operative in Pakistan some weeks ago.
But did the e-mails on the captured PC refer to an old plan or to an operation still being planned, to an aborted plan or a plan now under way with teams ready to go? And if so, when was it timed for?
The intelligence services did not know. They could not tell New York police commissioner Ray Kelly when to expect an attack. Mayor Michael Bloomberg referred rather testily, twice, in briefing the city's media, to the fact that there was no 'time-line' and that people should go to work as normal, which they mostly did, though many took a day off or worked from home.
Was there a degree of scepticism in the New York mayor's office? President George Bush said yesterday that "I hope the people of New York realise that by showing the intelligence we are better prepared," which seemed to indicate that the people of New York, in the form of the mayor perhaps, had expressed doubts about the whole thing.
Certainly the information put out in Washington by an unnamed senior intelligence official was really scary. According to a transcript of the briefing, he said it was "chilling in its scope, in its detail, in its breadth".
It was like finding out somebody had broken into the house and detailed how best to come back and attack, he said.
The "treasure trove" of information from the PC and other interrogations showed that al-Qaeda had conducted incredibly detailed surveillance.
They noted whether security personnel were armed, when they were on duty, what uniforms they wore. They logged numbers of employees, the types of shops, churches, schools, libraries, hospitals, police and fire departments nearby, and whether buildings had intercom systems or surveillance cameras.
In one case they recorded midweek pedestrian traffic counts of 14 people per minute on each side of the street.
They even noted the incline of underground car parks and the height of ceiling where a vehicle might in fact be detonated.
The intelligence official said this effort dated from before 9/11 and had been going on for quite some time, probably by many individuals. So was it old information? The intelligence official did not say.
Mr Bloomberg and New York Governor George Pataki went to the stock exchange yesterday to ring the opening bell and show defiance.
New Yorkers have got to get used to it it seems. There will be even tighter security for the Republican National Convention at the end of August and it will undoubtedly go on until after the election on November 2nd.