THERE is an old story about former Taoiseach John A Costello meeting a young barrister who was also a TD on the steps of the Four Courts back in the 1960s.
"Oh, you're down here now as well? Ah sure if you ever get thrown out of one big house - you can always go back to the other one," the former Fine Gael Taoiseach and career barrister joked, reflecting on the good of a safety net in the perilous game of politics.
The world over, many lawyers end up in politics and find it a good mix of law-making and practice in how law is applied. But when law and politics collide it is not always such a happy occasion.
The idea of parliament taking on powers of investigation is one of those potential unhappy collisions. The judiciary assiduously guard their powers to make judgment in law cases and they are not keen on parliamentarians' yen to take powers of investigation and judgment upon themselves.
The history of this is at best good - especially when it comes to Oireachtas committees efforts to investigate, interrogate and make findings in controversial issues. The 1971 case of Paraic 'Jock' Haughey, brother of former Taoiseach Charles Haughey, is always recalled.
He halted the Public Accounts Committee's investigation into what happened money intended for distress relief in the North at the time of the 1970 Arms Crisis.
The principle was enlarged by a Supreme Court ruling in the Abbeylara case in 2002 which said the Oireachtas was a legislature and not a court. Oireachtas committees had no power to inquire into alleged wrongdoing on the part of individual citizens, as opposed to inquiring into matters of public interest generally.
These cases, and other controversies recently involving the Public Accounts Committee, leave the bank inquiry committee with a limited room to manoeuvre.
But they believe that they have the legal formula to allow them function and conduct a meaningful and informative inquiry without impugning any individual in the process.
Central to that is the committee experts' plan to frame strict terms of reference which would allow them to compel everybody of interest to come and testify before them. Any challenge by somebody resisting the compulsion would inevitably end up in court where the relevance and necessity of a witness would be tested.
For this and other reasons this banking inquiry will take place under the shadow of the courts of law.
Sometimes the relationship between John A Costello's two "big houses" is very tricky indeed.