In the end, instead of petering out in a welter of legal submissions, the Public Accounts Committee's inquiry into the evasion of DIRT served up an extraordinary human drama. Just as it seemed that the stakes - tens of millions of pounds - could hardly get any higher, a new currency - personal reputations - was placed on the table. Instead of looking only at bogus bank accounts, the PAC has been asked to look at allegations of bogus evidence.
An allegation that key figures in the taxation department of AIB invented a crucial part of the bank's story initially arose in the cross-examination of Tony MacCarthaigh by Dermot Gleeson SC for the bank. Mr MacCarthaigh said, almost in passing, that the first of two phone conversations with him that are referred to on AIB files "may or may not have taken place".
Mr Gleeson pounced on this and asked him if he was "suggesting that it didn't take place". At first, Mr MacCarthaigh was far from emphatic: "I think it is a distinct possibility. I certainly can't remember it."
As the exchanges between the two men became more combative, Mr Gleeson reformulated the allegation, asking the Revenue witness whether he was claiming that Jimmy O'Mahoney in AIB's taxation department had invented "the content of a phone call which may or may not have taken place". Tony MacCarthaigh replied: "I'm not in a position to say whether it was invented or whether it was a misunderstanding. I'll leave both options on the table."
At this stage, then, the allegation existed as no more than a strong implication. As such it might, in the overall scheme of the PAC's deliberations, have been allowed to subside into obscurity. Instead Eoghan Fitzsimons, in his cross-examination of the bank's key tax advisers on behalf of the Revenue Commissioners, made it not just an explicit charge but a central plank of his argument. Suddenly an abstract accusation that an institution had acted in bad faith became, on live television, a direct attack on the credibility of respected professionals.
From early on in his questioning of the first of the AIB witnesses, the tax compliance manager Deirdre Fullen, Mr Fitzsimons laid out a scary scenario. As he sought to suggest, the AIB tax advisers were facing a potential nightmare. DIRT had been allowed to accumulate. The bank could be facing a tax bill of anywhere between £35 and £100 million; certainly a large chunk of its annual profits.
If this was recorded as an actual liability, AIB would have to issue a profit warning to the Stock Exchange. The bank's share price, already "at a very low ebb", would tumble.
And so, he suggested, "the people at the top of AIB would have been asking questions as to how did it arise". They would want to know "whether the tax department did its job properly". The people who ran that department would have been very worried that they were going to get the blame for a major disaster.
This contention was categorically rejected by the bank witnesses. Deirdre Fullen said that "that thought never entered my head". Donal de Buitleir questioned whether there would have been implications for the share price at all and insisted in any case that "AIB is not an organisation which, in my experience, operates what I would call a culture of blame."
Eoghan Fitzsimons persisted, however, with a line of questioning that relied on the basic assumption that the people in charge of AIB's taxes had a strong motive to make it seem that the bank didn't really owe huge sums of money at all because the Revenue had agreed effectively to write off the money.
This was the context for his allegation that the supposed amnesty was invented, and that the bank's internal files were arranged to make it look as if this alleged invention was real.
In order to support this very serious claim, he placed the actual documentary record under a relentless forensic microscope. Instead of asking merely who said what to whom, he asked how and when these documents came into being.
It should be stressed that the AIB witnesses completely and unwaveringly rejected this allegation. Each of them maintained that the documentary record that the bank compiled was an accurate account of real discussions. And no evidence of a conspiracy to concoct a fictitious amnesty has emerged in the course of the PAC's exhaustive hearings. The AIB witnesses were, however, unable to account for certain aspects of the documentation.
The first focus of Eoghan Fitzsimons's attention was one of the most familiar documents in the inquiry. Drawn up by Deirdre Fullen, it is headed "Summary of meeting with Investigation Branch on 13th February". This document was intended, essentially, to inform the incoming financial director of the bank, Kevin Kelly, of the situation with regard to DIRT. It contained the apparently wonderful news that the Revenue had agreed to an amnesty.
The problem with this document, however, is that it contains material which AIB itself agrees did not originate at the February 13th meeting but in the later, bitterly disputed phone call between Jimmy O'Mahoney and Tony MacCarthaigh. Under insistent questioning, Deirdre Fullen, while insisting that she had not meant to mislead anyone, accepted that the document was not, in fact, an accurate record of the February 13th meeting:
Q: You gave him an inaccurate version of the meeting. Isn't that so?
A: OK, on that basis, I did.
Q: You agree?
A: I take your point, yes.
Donal de Buitleir, the group head of taxation, was unable to say why he passed on this inaccurate record. Asked whether he knew that it "did not contain a correct account of the meeting", he said: "I can't say I thought about it at the time."
The second key issue on which Mr Fitzsimons attacked the credibility of AIB's documentation was that of the crucial phone call itself. In spite of its immense significance for the bank, allegedly saving them tens of millions of pounds, the only record of this call is a tiny memo dictated by Jimmy O'Mahoney, group taxation manager, to Deirdre Fullen on February 26th 1991.
It says simply: "J.O'Mahoney telephoned D.A. McCarthy for clarification re the penultimate paragraph of his letter dated 15th February 1991. D.A. McCarthy confirmed that, if relevant, any DIRT payment to be negotiated would relate only to that on interest paid subsequent to 5th April 1990." For AIB everything hinges on these few lines of type.
Under cross-examination, Jimmy O'Mahoney suggested that he probably made the phone-call on the morning of February 26th. Eoghan Fitzsimons then produced a long memo hand-written that afternoon by Mr O'Mahony to one of the bank's most senior executives, Brian Wilson.
Mr Wilson had called Mr O'Mahony, asking to be filled in on "what has been going on with Revenue". Yet in his detailed reply to Mr Wilson, Jimmy O'Mahoney did not refer at all to the phone call which he believes took place that morning and which had a crucial bearing on the whole issue.
"Why", asked Eoghan Fitzsimons, "in the memo did you not say to Brian Wilson that you had, that morning, received confirmation from Mr McCarthaigh that, if relevant, any DIRT payment to be negotiated would relate only to that on interest paid subsequent to 5th April 1990? Why did you not put that in this handwritten memo which you sent to Brian Wilson, a very important man in the bank?" There was a long silence before Jimmy O'Mahoney replied: "I don't know."
Eoghan Fitzsimons then suggested that "the only logical explanation is that the telephone conversation had not taken place at all and that the memo is in fact a, well, not to put too fine a tooth on it, a fiction."
Mr O'Mahoney replied: "I disagree totally with you."
In his final submission on behalf of AIB, Dermot Gleeson SC called on the committee to explicitly reject the contention that bank staff had invented a fictional account of what transpired between themselves and the Revenue. This demand makes it difficult for the PAC to turn away from what must now be, for all concerned, an extraordinarily painful aspect of the whole saga. In the end, after two gripping final days, even more than money is at stake in the PAC's final report.
Fintan O'Toole is at fotool@irish-times.ie