Experienced O'Brien is no stranger to high-level clashes
GARDA Ombudsman chairman Simon O'Brien brought a wealth of experience to the job when he was appointed three years ago.
He made the move from the Garda Inspectorate's office, where he was deputy chief inspector since 2010.
While working with the Garda Inspectorate, Mr O'Brien led inspections into garda investigations of child sexual abuse and frontline garda supervision.
During his tenure as chair of the garda watchdog, he has been faced with the most tumultuous time in recent garda history.
The Garda Siochana Ombudsman Commission (GSOC) is carrying out an investigation into the penalty points scandal and it is also reviewing claims of malpractice by garda whistleblower Maurice McCabe.
Mr O'Brien clashed with former Garda Commissioner Martin Callinan when he accused garda management of failing to co-operate with his investigations.
He claimed GSOC's investigation into collusion between detectives and convicted drug dealer Kieran Boylan was hampered by delays in getting information from gardai.
Mr Callinan hit back, saying there would be "bodies lying all over the country" if sensitive information on garda matters was not handled properly by his office.
The GSOC bugging affair stemmed from a breakdown in communications between the Garda Ombudsman and senior gardai.
Mr O'Brien and his colleagues feared their offices were bugged during their investigation into Mr Boylan.
Mr O'Brien was called before former Justice Minister Alan Shatter when the bugging allegations first emerged in February.
However, after this meeting, Mr O'Brien's account of the surveillance sweep in the Ombudsman's headquarters clashed with Mr Shatter's version of events. Mr O'Brien said he could not rule out a security breach in the Dublin city centre office, while Mr Shatter dismissed the allegations as "baseless innuendo".
Taoiseach Enda Kenny was forced to step in and order an investigation into the affair.
It was previously reported Mr O'Brien commutes between London and Dublin on a weekly basis.
The chairman, who earns around €150,000 a year, spends between two and three days in Dublin each week.