The former Guinness & Mahon accountant, Mr Padraig Collery, gave documents of "critical relevance" to the tribunal to his ex-secretary for safe-keeping two months ago, the tribunal heard.
Ms Margaret Keogh, clerical assistant to Mr Collery at the bank, was given the documents - which gave a key to decoding the Ansbacher depositors' names - last November.
She brought them to her solicitor, who thought they were relevant to the tribunal and informed the tribunal's solicitor.
Mr John Coughlan SC, for the tribunal, said an order was made for production of the documents. The tribunal would now be asking why "this information and these documents were not brought to the attention of this tribunal, and as to what prompted the continuing secrecy surrounding the operation of these accounts".
Earlier Mr Coughlan noted that in three days half of the paper records of the Ansbacher operation were destroyed by Mr John Furze with Mr Collery's help.
