There is a certain delicious irony in hearing leading Irish bank officials rue the day they secured an unwritten agreement with the Revenue Commissioners not to trawl back through its records on DIRT.

After all, anyone who has conducted business with the banks over anything as simple as opening a current account or securing an ATM card will be familiar with the amount of paperwork the bank feels it necessary to have the customer complete. Strange, then, that on a multimillion pound issue such as DIRT evasion, AIB tax officials should be happy with the "nod and wink" approach adopted in its hotly disputed "deal" with the Revenue.

When pressed at the Dail Committee of Public Accounts inquiry as to why no written agreement was requested, the bank pointed out that it understood the Revenue officials were acting on the instructions of their superiors, but that it was sensitive to the fact that a written agreement might have put the Revenue in a difficult position vis-a-vis the law. You see, the Revenue had no powers to sanction such a tax write-off.

Ah, that explains it then. So, let me get this straight. AIB and its officers had no problem cooking up a deal with the Revenue to avoid paying tax - if AIB's version of events is to be believed - but did not want a paper trail that might lead back to it.

It is hard to see what the Revenue stood to gain and, therefore, why it would agree to any such scheme. Of course, there is always the issue of why it did not pursue AIB for the back taxes owed . . .