Denis O'Brien's Supreme Court Appeal will be heard today as part of a landmark privacy case.
The businessman says TDs abused Dáil privilege when they spoke about his finances in Leinster House.
He claims Kildare TD Catherine Murphy and Pearse Doherty had no right to reveal court protected details about his dealings with State-owned bank, IBRC.
Last year the High Court ruled against him.
Our Courts Correspondent Frank Greaney reports on today's action: