Businessman Denis O'Brien has begun his application for an order directing a public relations firm to identify the client who commissioned them to compile a dossier about him.
Mr O'Brien claims Red Flag Consulting, Chief Executive Karl Brophy, Chairman Gavin O'Reilly and three other members of staff are involved in a conspiracy to harm his interests.
Mr O'Brien says they compiled and authored a dossier about him containing defamatory material on the instructions of a client.
He alleges the defamatory statements about him in the dossier include a statement that he used philanthropy as a PR tool and a description of him as Ireland's Berlusconi.
Senior Counsel for Mr O'Brien, Michael Cush, said the dossier contained evidence of very serious wrongdoing on the part of Red Flag and the client.
Mr Cush said they had always maintained that the wrongdoing consisted of conspiracy.
He said the conspiracy could involve one or more people who are doing something unlawful.
He said if two or more people came together to do something lawful with the purpose of trying to harm someone then that was something that was actionable in court.
Mr Cush said it was clear the predominant objective of the dossier was to injure Mr O'Brien.
He said the dossier was replete with defamation.
He told Mr Justice Colm Mac Eochaidh that if he compiled a dossier with someone else of material that was not in itself defamatory, but with the intention of harming another person, then that was an unlawful conspiracy.
Mr Cush said that was the law.
Mr Cush said the defamation involved allegations about Mr O'Brien's philanthropic activity, his interests in Haiti and his media interests.
He said the documents authored by Red Flag repeated allegations about Mr O'Brien's interests in Haiti that had already been found to be defamatory by a jury.
Red Flag claims the material in the dossier is already in the public domain.
It claims the material simply paraphrases and summarises what is already in the public domain.
It strenuously denies anything in the dossier is defamatory and denies that it was engaged in a conspiracy to damage Mr O'Brien.
Mr Justice Mac Eochaidh said to get the kind of order they are seeking, Mr O'Brien's lawyers had to persuade him that the unnamed client wanted to damage Mr O'Brien.
He asked if the client's instructions could simply have been that he or she wanted to invest in an O'Brien company and wanted to know everything about him.
Mr Cush said there was no attempt to present an objective picture.
Lawyers for Mr O'Brien said a draft speech prepared for Fianna Fáil TD Colm Keaveney was the most significant document contained in the dossier.
Mr Cush said their IT experts had identified amendments to Mr Keaveney's speech authored by Red Flag Chief Executive Karl Brophy and director Seamus Conboy.
Mr Keaveney did not adopt these amendments in the speech he actually delivered, the court heard.
Mr Cush asked if the amendments could have been made for any other reason other than to make people think less of Mr O'Brien.
He said the document showed the lengths to which the defendants were prepared to go to to put out a negative message about Mr O'Brien on the instructions of their client.
Mr Cush said it had always been Mr O'Brien's case that Red Flag was doing this with a view to disseminating or publishing the dossier.
He said Red Flag had never denied that it had disseminated it.
He said Mr O'Brien had noticed an unusual pattern of journalists ringing up with the same inquiries suggesting they had been prompted by someone.
He said the defendants had a paying client and the essence of its business was communications.
He said Mr O'Brien's experts' analysis of the dossier showed the defendants had been working on it as far back as May 2015, five months before Mr O'Brien discovered its existence.
Mr Cush added that the attempts to make amendments to a speech to be delivered by Mr Keaveney showed an intention to publish.
Red Flag has described claims by Mr O'Brien that Gavin O'Reilly was an active player or influence in creating the dossier as "entirely speculative".
It also accuses Mr O'Brien of a lack of candour about how he received the dossier.
In a second sworn statement, Mr O'Brien said he had hired chartered accountant John Whelehan, now working in Kiev, Ukraine, but formerly with accountancy giant PwC, to investigate publicly available material related to him and his businesses to see if the source of the suspected campaign could be identified.
He did not get a report from Mr Whelehan because, in the interim, he received the dossier anonymously on a USB memory stick in an envelope with no postmark received by him last October in his Dublin office.
Mr O'Brien says a code to decrypt the stick was written inside the envelope and he learned from the dossier itself of Red Flag's alleged involvement in the alleged campaign.
Mr Cush said that if Mr O'Brien's first sworn statement lead Red Flag to believe it was from the investigation, rather than the dossier itself, that he got his belief about Red Flag's alleged dissemination of the dossier, that was incorrect and Mr O'Brien apologises for that.
Senior Counsel Michael Collins for Red Flag, said this matter was "not as simple" as Mr Cush outlined and he would address the claim of lack of candour in continuing arguments before Mr Justice Mac Eochaidh on Friday.
Earlier, Mr Collins said it was "genuinely difficult" to know exactly what form of order was being sought by Mr O'Brien.
