Thirty police and anti-terrorist officers, some of them armed, arrested the three men in a series of meticulously planned and precisely executed dawn raids in Edinburgh.
The men are believed to have lived together, maintaining a low profile since moving to the city from west London in September this year.
The flat at which they are understood to have lived most recently, in Easter Road, was raided and searched at exactly the same time as two other properties in Albion Road and Piersfield Terrace.
The operation, which had been two months in the planning, was co-ordinated by Lothian and Borders Police, backed by the security service MI5 and the Metropolitan police.
Almost simultaneously four other men were arrested in a similar operation in London.
It was only after the shock of the Edinburgh raids had subsided that a neighbour recalled something unusual about one of the flats where the men are understood to have lived.
A satellite telephone dish - allowing signals to be sent to, and received from almost anywhere in the world - had been set up in the Albion Road apartment. The neighbour remembered that whatever the weather, even when it was bitterly cold outside, the window in the room where the equipment was stored remained open.
Gordon Crowe, who owns a garage in Edinburgh’s Albion Road, said he had seen the equipment last month.
"About a month ago I spotted a satellite phone aerial and dish inside the flat," he said.
"In that particular room the window was always wide open, even in the coldest weather, and I always thought that it really strange."
The three men seized on Wednesday are now being held under the Prevention of Terrorism Act at the high security police station in Govan, Glasgow, one of the national holding centres for suspected terrorists. They are expected to make their first formal appearance in court on Christmas Eve.
But the raids did not end with those carried out on Wednesday. Yesterday morning police raided and searched two other addresses in Albion Road and Broughton Road. No more arrests were made.
Sources have revealed that investigating officers have a mountain of information to sift through. The men are being interviewed through interpreters . A police source admitted: "It’s just one massive jigsaw."
Investigating officers are also tapping into Edinburgh’s Muslim community to gather information.
Shami Khan, from the Edinburgh Pakistan Society, said: "They have been asking if any strange faces had been noticed. Of course we are co-operating with them."
On Easter Road neighbours recalled how the "quiet and polite" 30-somethings had tried to enrol, unsuccessfully, on an English course. The group lived together in a two-bedroom flat and neighbours initially thought they were students or asylum seekers.
After settling into Edinburgh the three men appeared keen to integrate themselves into the local community, buying their halal meat from a Syrian butcher on Leith Walk and attending various mosques in the city.
A neighbour said he started seeing the trio "milling around" from the middle of September this year: "They were always together, the three of them. They were very quiet and polite and went out most of the day during the week in their suits."
He added: "They used to mill about in the stairwell at the weekends. I used to think it was a bit strange that the three of them were living in a two-bedroom flat but they were never any bother."
Margaret Fraser, 70, who lives two doors along from the Easter Road address where the three suspects were arrested said she had spoken to two of the men on several occasions in the last month.
Fraser added: "Their English wasn’t great but I could understand what they were saying. They were very polite to me.
"There was never any bother with them. They left the flat usually at 7am in the morning, all dressed in suits and returned at about 5.30pm in the evening."
But despite the run-of-the-mill picture painted by neighbours, the rumour mill has been buzzing since Wednesday’s raids, and ratcheted up once again by those carried out yesterday.
The alleged terrorist dimension has spun off a series of rumours ranging from far-fetched plots to poison Edinburgh’s water system to speculation that the Scottish capital was a base for terrorists to plan al-Qaeda activities across the UK and Europe.
But the most horrifying claim of all - and potentially the most damaging for the event which is expected to attract some 100,000 revellers this year - is that of a plot to mount a double bomb attack on Edinburgh and London’s Trafalgar Square.
Edinburgh’s Hogmanay celebration is known across the world. As the highest-profile New Year’s festival in Europe and attracts an international crowd of partygoers.
Even rumours of a terrorist plot could cause huge economic damage to Edinburgh. The New Year celebration is one of the biggest in the world, arranged around a four-day carnival of events, and is estimated to boost the local economy by 36m.
Last night police moved quickly to dismiss the claims - made by an MI5 source - as baseless. And civic leaders attempted to damp down the fears the arrests and raids had generated.
The MI5 insider told Scotland on Sunday terrorists had planned to plant car bombs, similar to the one used to devastating effect outside a Bali nightclub as close as possible to the throng of revellers.
But Deputy chief constable of Lothian and Borders Police, Tom Wood said there was no evidence that anywhere in Scotland, let alone Edinburgh specifically, was a target for terrorists.
On the arrests, he commented: "We are in the process of gathering information. The men are being held and interviewed and will appear in court in Edinburgh on Tuesday when we will apply to hold them for another seven days. They may be charged or they may be released."
And Edinburgh Council yesterday insisted it had no plans to change this year’s Hogmanay street party.
"At this stage we have not been alerted to any specific threat to Edinburgh’s Hogmanay celebrations.
"The message we want to put across is that we are much open for business and looking forward to a fantastic Hogmanay."
Councillor Donald Anderson, leader of the City of Edinburgh Council, said they had been advised there was no evidence of a terrorist threat in Edinburgh.
He said: "The capital has lots to offer this Christmas and Hogmanay and we’re looking forward to welcoming visitors from near and far to come and enjoy all the festivities."
But the recollections of neighbours and forthright police denials have done little to quell speculation, fuelled by successive warnings from the British government that Britain is high on the list of al-Qaeda targets.
Amid the claims and counter-claims, the public could be forgiven for feeling a sense of confusion about the true nature of the terrorist threat facing Scotland and the rest of the UK. September 11 was a clear demonstration of terrorists’ willingness and ability to pull off the unimaginable.
Security sources and terrorist experts agree that Edinburgh’s Hogmanay party would have provided an ideal, soft target for terrorists desperate to follow up the obscenity of September 11.
Cars loaded with explosives could conceivably be parked near barriers marking off the street party where tens of thousands of people with special street passes gather in the centre of Edinburgh to see in the New Year. David Capitanchik, a terrorism expert at Aberdeen’s Robert Gordon’s University, said: "The model for such an attack would be the suicide bomb attacks which we have seen in Israel and which have had such a devastating effect.
"As we have seen in the Middle East, terrorists like to target popular holiday periods, such as Yom Kippur, Passover, Christmas, and the New Year. People are more likely to be off guard, and unsuspecting, an attack at a holiday period is seen as demoralising and shows the population just how ruthless their terrorist enemy is."
It will be some months before the true story behind the arrests in Edinburgh emerges. In the meantime, for the capital, the message is the party is still on for December 31.