It's a common device in thriller movies to let the viewers know that the secret the baddies are trying to hide is, unknown to them, contained in boxes and boxes of information stored in some huge underground archive.

A crucial part of the plot then resides in the efforts of the character who persists in the seemingly hopeless task of finding the needle hidden in the huge, indexed haystack. Just when the hero is beginning to feel he might be bested by the baddies, in bursts his associate clutching a few sheets of paper from the archives. From there it's straight to the denouement.

The whole saga of the uncovering by the McCracken and Moriarty tribunals of the way Charles Haughey was secretly bankrolled by rich businessmen has depended hugely on this sub-plot.

Mr Haughey's bagman, the late Des Traynor, managed to do what he did because he had control over the relatively small bank Guinness & Mahon. The downside to the bank's size, however, from Mr Traynor's perspective, was that it was able to hold information in its archives for longer than the larger banks.

Every so often the finance director with Guinness & Mahon, Sandra Kells, makes an appearance at the Moriarty tribunal and outlines her latest discoveries from the archives. Her latest was on Tuesday, and some of her evidence concerned a company associated with the multi-millionaire property developer, John Byrne.

The company, Princes Investments Ltd, runs the Mount Brandon Hotel in Tralee, Co Kerry. Through Mr Traynor, Mr Byrne organised a £116,000 sterling loan for Princes Investments from Guinness & Mahon in 1975. The loan was paid off with a transfer of £186,986 from the Ansbacher deposits 10 years later, in September 1985.

Ms Kells told the tribunal the statement which would have shown the Princes loan being paid off in September 1985 did not exist in the archive. "The only reason I can give [for this] is that a Guinness & Mahon executive removed the statement from the automated microfiching process," she said.

The tribunal suspects the statement was removed because it would form part of a trail going back to the Ansbacher deposits. If the company noted in its accounts that its loan had been paid off, and the Revenue began to inquire into where the money came from, it could, conceivably, discover Mr Traynor's secretive Ansbacher operation.

Despite the fact that the statement is missing, Ms Kells was able to piece together what happened in September 1985. Banks record each year the amount of interest accumulated by each loan account on their books, and Ms Kells used this information to calculate how much interest had accrued on the Princes Investments loan in 1985. She worked out that on September 4th, 1985, the loan account stood at £186,986 sterling.

This was precisely the figure recorded on what is called the bank's daily imput log for that same date as having been transferred from one of the main, general Ansbacher accounts to the Princes Investments account. Pooling the information from both sources shows that the loan was paid off in full on that date with money from the Ansbacher deposits.

When Mr Byrne was called to give evidence about this he stated that the loan had been paid off with offshore money without his being told. Moreover, he said that two years later he and his partner in Princes Investments, Thomas Clifford, paid £260,000 to Guinness & Mahon bank to pay off the loan.

It was, Mr Byrne said, a "crazy" situation, and he was at a loss to understand it. The only person who could have paid off the loan with his money without his express authority to do so was Mr Traynor, who was a trustee of his Ansbacher trust.

But the person who requested him to "pay off" the loan two years later was also likely to have been Mr Traynor. In other words, Mr Traynor knew what was going on in relation to Mr Byrne's money, but Mr Byrne knew nothing.

It is not the first time that Mr Byrne has expressed surprise at what the tribunal has discovered in relation to his own affairs.

Mr Traynor went to great lengths to hide his secret offshore operation. The tribunal has established that not only was the bank statement showing the Princes Investments loan being paid off in September 1985 removed from the bank's filing system, but bogus statements were produced purporting to show the loan still in existence.

Mr Traynor's second-in-command in relation to running the Ansbacher deposits in Guinness & Mahon, Padraig Collery, said in evidence that he "probably" produced those bogus statements using the bank's computers.

Not only that but he then knowingly used the bogus statements as the basis for issuing certificates to the firm of Haughey Boland & Co, the Princes Investments auditors, confirming the existence of the loans and the amount of interest charged thereon, for the following two tax years. This interest would have been charged against tax.

When £260,000 was paid over by Princes Investments on July 23rd, 1987, it was lodged to the account of Amiens Securities Ltd in Guinness & Mahon. This account was controlled by Mr Traynor, and money has been shown to have been transferred from it to Mr Haughey.

The £260,000 lodgment brought the balance on the account to £267,649. Five days later there was a cash withdrawal of £6,149. The following day there were five withdrawals. Two debits totalling £48,000 were transferred to another Amiens account in the bank.

Another two debits, totalling £40,000, were for drafts payable to the account used by Haughey Boland & Co to pay the personal expenses of Mr Haughey. There was also that day a £20,000 withdrawal used to fund a draft made out to cash. The following year there were further transfers from the account which were for Mr Haughey's benefit.

Further evidence was heard this week of money associated with Mr Byrne going to Mr Haughey. On February 18th, 1987, the day after the general election which saw Mr Haughey returned to the office of taoiseach, Mr Byrne wrote out a cheque for £50,000. The cheque was made out to Guinness & Mahon, and Mr Byrne couldn't remember writing it or what it was for. He said he must have given it to Mr Traynor. The cheque was lodged to the Amiens account.

Mr Byrne has been doing business with Haughey Boland since the early 1960s and said he was a very good friend of Mr Haughey's, having known him for 40 years. However, despite being so close to both Mr Haughey and Mr Traynor he insists that not only has he never given money to Mr Haughey, he has never been asked to do so.

Mr Byrne said: "Mr chairman, I'd like to categorically state that I have never given Mr Haughey a penny or a pound in my life and I made that statement the first day I went in to see the tribunal in private, and he has never asked me for a penny in his life."

Asked if Mr Traynor or anyone else had ever asked him for money for Mr Haughey, he said: "Never."

Mr Byrne has appeared a number of times before the tribunal. As he was leaving the witness box on Wednesday Mr Justice Moriarty asked him if it would be "fair to say there has been a considerable amount of lack of recollection" on his part. Mr Byrne, who is 80 but still active in property development in Dublin, said: "We all get on."