By John Ware
BBC Panorama reporter
Twenty nine people and unborn twins died in the bomb attack
Entering 10 Downing Street two days after the Omagh bombing, the-then Irish Prime Minister Bertie Ahern said that both governments had to ensure their respective police forces work closely "to make sure we do every single thing we can to make sure the people involved in this are crushed".
Thereafter ministers from both governments gave regular public assurances that the Royal Ulster Constabulary (RUC) and An Garda Siochana, Ireland's police service, were effectively joined at the hip.
"I can say that the actual working together of the Gardai and the Royal Ulster Constabulary, and the [security] services either side of the border, has been immensely close" then UK Prime Minister Tony Blair told Parliament three weeks into the hunt.
Assistant Commissioner Kevin Carty, in overall charge of the Gardai inquiry, has said that "never before in the history of the two organisations had there been closer co-operation", adding that the Gardai investigation had been "conducted with as much energy and as many resources as if the bomb had gone off in the South".
In reality, there were two separate and parallel inquiries.
That was the verdict of an internal review conducted by one of the RUC's most senior detectives, Chief Superintendent Brian McVicker and it was endorsed by Her Majesty's Inspector of Constabulary who said this simply "acknowledges fact".
The failure to conduct what Ch Supt McVicker says should have been an "open and joint inquiry" helps explain why today no-one is behind bars for the Omagh bombing.
Although the crime was in Northern Ireland, RUC analysis of mobile phones used in the preparation and execution of the bombing showed most of the suspects lived in the Republic of Ireland.
Of the 22 suspects whose telephones were active in Omagh and four bombings linked to it, 18 were resident in the Irish Republic, just four in Northern Ireland.
So although the RUC had primacy because the crime was committed in their jurisdiction, they were often powerless to influence the course and direction of the Gardai investigation.
Intelligence sharing was sometimes nonexistent. No formal protocol existed between the two forces to manage the exchange of documents and information.
The two forces had different rules, laws and investigative strategies:
"Formally asking for things was slow and cumbersome," said one senior RUC officer. "Requests had to go to Dublin."
Tony Blair and Bertie Ahern promised close co-operation
So getting information quickly depended largely on personal relationships, which was why the then RUC Chief Constable Sir Ronnie Flanagan appointed his most senior detective, Chief Superintendent Eric Anderson as Task Force Commander, to liaise with the Gardai.
"The way it worked with the Gardai generally," Ch Supt Anderson has said, "was that if they liked you, you got stuff. If they didn't, well, you didn't".
There was mutual trust and respect between Ch Supt Anderson, Assistant Commissioner Carty and his right-hand man Detective Inspector Tadgh Foley.
It was "obvious" says Ch Supt McVicker that Ch Supt Anderson's relationship with the Gardai was "invaluable at various stages of the investigation."
As detectives, Assistant Commissioner Carty and Det Insp Foley were also held in high regard by the RUC.
But their relations with the senior investigating officer, Detective Chief Superintendent Hamilton "Hammie" Houston and his deputy, Detective Superintendent Brian McArthur, were sometimes frosty.
Ch Supt McVicker says that arrests by the Gardai were sometimes executed without consulting or even telling Det Ch Supt Houston.
No details of interview strategy were forwarded to Det Ch Supt Houston in advance.
In the case of three key suspects, while the Gardai did question them, they did not pass on the details of what they said to the RUC.
After six months, the Gardai did charge veteran republican Colm Murphy with conspiracy to cause explosion and he was convicted. But, following an appeal, even he is free again pending a retrial.
After 19 months, the RUC began a review of their own inquiry to see if it was heading in the right direction. Ch Supt Anderson asked Assistant Commissioner Carty if the Gardai might consider doing the same, perhaps even a joint review? Assistant Commissioner Carty had a terse response: "It's a non starter."
On the eve of the bombing's first anniversary in August 1999, a lunch was arranged for senior officers from both inquiries at a hotel in Omagh.
Tensions were already simmering because Det Ch Supt Houston had extended his request for intelligence "'pen pictures" of suspects to all known republican dissidents living on the Republic side of the border. This request had been outstanding for four months.
Because Det Ch Supt Houston and Det Supt McArthur were irked by the refusal of the Gardai to review their inquiry, Ch Supt Anderson had cautioned them "to go easy" at the lunch.
Ch Supt Anderson is said to have told his colleagues: "We're not getting a review out of them and that's it. There's nothing we can do about it."
The atmosphere was cordial until Det Ch Supt Houston and Det Supt McArthur reminded the Gardai of their request for more "pen pictures" so they could store them in the RUC inquiry's database.
Unwilling to share
The senior Gardai officer present was Detective Chief Superintendent Dermot Jennings, head of the Gardai's Crime & Security branch, the Republic's equivalent of Special Branch.
"There will be no pen pictures!" snapped Det Ch Supt Jennings and according to one officer present "the whole atmosphere changed".
Many suspects lived in the Irish Republic under Garda jurisdiction
But Det Ch Supt Houston and Det Supt McArthur are said to have pressed Det Ch Supt Jennings and it "began to get quite nasty."
Det Ch Supt Jennings is reported to have said: "Look, a lot of these people are our sources. We don't discuss this. In these files there are things we would not want you to see. We will tell you anything we think is relevant on a need to know basis. We do not want a review. We do not have disclosure in the South like you do in the North."
The Gardai was concerned that, in the event of charges, a review would lead to court applications by the defence for material about their network of informers. "We could end up with bodies all over the place" said Det Ch Supt Jennings.
"That was it," said the source. "End of discussion."
In his review, Ch Supt McVicker commented that the Gardai decision was "regrettable as the details requested were crucial to the RUC investigation". It was "difficult to understand the concerns over disclosure" because the information would have been given legal protection.
At the lunch the Gardai did agree finally to arrest Liam Campbell, the "Officer Commanding" of the Real IRA.
However, he was not arrested for another nine months, even though he had been a firm suspect for two-and-a-half years and the RUC's telephone analysis pointed to him being at the heart of Omagh and other linked bombings.
In December 2000, in a joint statement, Tony Blair and Bertie Ahern said there was a "model of co-operation between the RUC and the Gardai".
And yet when it came to the key suspect, Seamus Daly - who the RUC believed had been the "hands-on" organiser of the bombing - there was nothing to show he had even been questioned by the Gardai about the mobile phone analysis that pointed to his role.
Even the Gardai themselves had been in possession since September 1999 of intelligence that Daly had been in the bomb car.
When in May 2002 Detective Superintendent Norman Baxter was appointed senior investigating officer of a newly invigorated inquiry by the renamed Police Service of Northern Ireland (PSNI), relations did improve but this was short lived.
By July, Det Supt Baxter had no choice but to investigate claims by a Garda Detective Sergeant John White that shortly before Omagh, Det Ch Supt Jennings knew republican dissidents were looking for a car to steal for a "spectacular" in Northern Ireland but ordered that it be allowed to cross the border to protect a Gardai informant.
Det Supt Baxter eventually concluded Det Sgt White was lying, but the damage between the two forces was done.
So strained were relations that by 2003, it was no longer clear to the PSNI how many officers the Gardai were committing to their inquiry. "It's very small" one officer told me at the time.
Bomb car receipt
In February that year, some PSNI officers believe the Gardai had scuppered their efforts to bring Daly - who lived just south of the border - to trial in the North.
Besides the phone analysis showing that the mobile registered to Daly had been linked to car bombings in Lisburn and Banbridge and the theft of the Omagh bomb car, PSNI officers had also recovered a receipt for the bomb car used in Banbridge from a scrap yard at Crossmaglen.
Forensic analysis showed the name "Daly" had been scratched out.
The Gardai had also obtained a signed statement from the accountant who identified Daly's voice as having called him on the mobile that just 71 minutes earlier had been active in Omagh when the bomb car was parked.
The PSNI wanted to question Daly in the hope that the Public Prosecution Service for Northern Ireland would "give the case a run".
Daly had a habit of venturing into Northern Ireland to go drinking. The PSNI planned to arrest him when he came across the border so they asked the Gardai to tip them off when he was heading their way.
PSNI sources say the Gardai agreed - only to arrest Daly themselves without informing the PSNI Inquiry team.
The first Det Supt Baxter got to hear about it was when Daly appeared in Dublin on a charge of IRA membership - a minor matter compared to mass murder.
"There was a lot of anger at headquarters about this" said a PSNI source in Belfast. "The ACC [Assistant Chief Constable] crime was not normally an angry man but I never heard him so angry."
Daly served just two-and-a-half years.
Today he runs a scrap metal business - buying smashed up cars for next to nothing, rebuilding them and selling them to the developing world.
And he enjoys the good life sometimes to be seen with his girlfriend, a nurse, drinking at his local.
Despairing at the failure of the two police inquiries some Omagh families are seeking redress in the civil courts.
Gardai officers have been giving powerful evidence on their behalf. However both Assistant Commissioner Carty and Det Insp Foley - the Gardai inquiry's two most prominent detectives - have declined to answer questions from the BBC, even though both are now retired.
Much is now known about the police inquiry in Northern Ireland because it has been reviewed not just internally by the PSNI's own officers, but also by HM Inspector of Constabulary, not to mention the Policing Board, the Police Ombudsman and officers from Merseyside.
The PSNI is probably now one of the most accountable in the world. But the Gardai Inquiry? Much of what they did and why, remains wreathed in mystery.
Panorama: Omagh - What the Police Were Never Told will be broadcast on BBC One at 8.30pm on Monday 15 September.