The Red Flag consulting firm being sued by businessman Denis O’Brien has confirmed it had a client for a dossier of material relating to the businessman which he alleges is part of a conspiracy to damage him, the High Court has heard.

A consulting company has told the High Court that billionaire businessman Denis O’Brien has left “clouded in mystery” exactly how material from the firm’s computer files ended up on a USB stick placed in an envelope sent anonymously to Mr O’Brien.