The unprecedented lawsuit, the first time evidence from a case in the North will be heard in the Republic, will see more than 50 Gardai called to testify.

Over the next two weeks, dozens of witnesses, including many detectives, will be called as the families of the Omagh victims seek €14m in damages from five men allegedly linked to the Real IRA.

Twenty-nine people, including a woman pregnant with twins, died in the Omagh bombing in August 1998.

Nobody has been convicted for the atrocity, but named on the lawsuit are 58-year-old Michael McKevitt, the alleged leader of the Real IRA, the man said to be his number two, Liam Campbell, and Colm Murphy, Seamus McKenna and Seamus Daly.

All deny any involvement.

The case is to be heard by District Judge Conal Gibbons in the presence of two judges from the North.

The multimillion-pound landmark action is being funded by public donations and money from the British Government.