The Commercial Court has begun hearing a multi-million euro legal battle between concert promoters Denis Desmond and Eamonn McCann.
The two men set up MCD together in 1980. McCann, who is based in Belfast,has now initiated legal proceedings in a dispute over the value of his stake in the business.
Lawyers are describing this as "a row between two gentlemen".
MCD has brought big-name acts to Ireland over the years, including U2, Oasis and Kings of Leon.
Belfast-based McCann has come to court over the terms of the sale of his stake in the business to Desmond in a multimillion legal row scheduled to last six days.
Mr Justice Brian McGovern noted this morning that mediation had previously been suggested.
He said he presumed the parties were aware that if the case plays out to conclusion they are unlikely ever to do business again.