Two witnesses who may hold key details on the identities of the Ansbacher depositors will be questioned by the Moriarty Tribunal next Friday.
One - the long-time secretary of the former Guinness & Mahon banker, the late Mr Des Traynor - is known to have been involved in issuing instructions concerning lodgments and withdrawals from the deposits.
Ms Joan Williams worked as Mr Traynor's personal secretary at the bank and moved with him when he left to become chairman of Cement Roadstone in 1986.
Mr Traynor controlled the accounts and handled the personal finances of the former taoiseach, Mr Charles Haughey. But it is not known how much Ms Williams knew about the Ansbacher beneficiaries. Her evidence is likely to be heard in private.
The tribunal will also question Mr Padraic Collery, who set up a computer system within Guinness & Mahon bank whereby information about the deposits could only be accessed by those with a secret password. Mr Collery took over the operation of the deposits after Mr Traynor's death in 1994. Before that, he ran a system of coded "memorandum accounts", operating to Mr Traynor's instructions.
It is thought Mr Collery knew the identity of at least some depositors as a result of direct contact with them.
According to a notice published in yesterday's newspapers, the tribunal - which is inquiring into payments to Mr Haughey and the former Fine Gael minister, Mr Michael Lowry - will take evidence "on oath from certain witnesses in order to ascertain the identities of persons, if any, connected with bank accounts and other financial transactions relevant to the Terms of Reference" of the tribunal.
Subject to representations, the evidence will be heard in private. The tribunal will also detail its interpretation of its terms of reference during the Friday hearing.
Ms Williams was interviewed by lawyers for the McCracken Tribunal, which examined payments to politicians by Dunnes Stores, but was never called as a witness. A note handwritten by her on the bottom of one of hundreds of letters from the late Mr Traynor to Mr Collery, examined by the McCracken Tribunal lawyers, first linked Mr Haughey directly to the deposits. The note, on a letter concerning the withdrawal of £25,000 sterling from the S9 account, read: "By hand to CJH, 30th of November 1993."
Mr Collery later confirmed to that tribunal that bank accounts coded S8 and S9 held funds for the former taoiseach.
After his departure from Guinness & Mahon, Mr Traynor kept records on the individual Ansbacher accounts in his Cement Roadstone offices on Fitzwilliam Square. Depositors seeking to make deposits or withdrawals contacted the office with their requests. Mr Traynor and Ms Williams would then send instructions from the office to Mr Collery.
The tribunal is involved in issuing fresh orders to banks for documentation on the finances of Mr Haughey and Mr Lowry.
