The Taoiseach, Mr Ahern, is due to take the stand in the Four Courts this morning as a witness in a defamation action he has taken against a Cork businessman.
Mr Ahern will return to Dublin, taking a break from the Northern talks in England, for the case, which has resulted from serious allegations made against him by Mr Denis O'Brien.
Mr O'Brien made allegations, which he recently withdrew, that Mr Ahern accepted a £50,000 bribe from him in 1989 in the car-park of the Burlington Hotel in Dublin. The allegations led the Taoiseach to bring the action against Mr O'Brien.
The case is listed for 10.30 a.m. in the Circuit Civil Court.
It is expected that a number of witnesses will give evidence on behalf of the Taoiseach.
Mr Ahern was due to leave the talks in Weston Park near Birmingham and return to Dublin using the Government jet. According to his spokesman, he will return to England immediately the case is over.
Mr O'Brien had privately alleged to the Flood tribunal that he secretly gave Mr Ahern £50,000 on behalf of a property developer, Mr Owen O'Call aghan, to help get planning permission for the Liffey Valley Shopping Centre.
Mr Ahern issued a strong denial when the allegations, which caused tension in the Coalition Government, were made public in April last year.
At the end of last month Mr O'Brien instructed his lawyers to withdraw his entire defence. Mr O'Brien told The Irish Times last week that he had decided to "walk away from the case". He said: "There is nothing in it for me. I was sucked into this. And I am now unsucking myself. I never mentioned Mr Ahern by name."
He said he had nothing against Mr Ahern. "I have nothing to get in any of this. I woke up one morning last week and asked myself `What am I at'?"
When Mr O'Brien withdrew his allegations, Cork-based Mr O'Callaghan said he was "pleased, but not surprised". Mr O'Callaghan said: "These allegations were outrageous to begin with and never had a shred of evidence to support them. They were deliberately constructed to inflict as much damage on my character as possible."
Mr O'Callaghan has said he will be proceeding with his own defamation action against Mr O'Brien and the Sunday Busi- ness Post, which first reported the allegations.