However, in two investigations conducted during 2005, neither the Independent Commission Against Corruption nor an independent consultant found impropriety regarding their relationship.

The departure of Gillespie, whose contract was evidently not renewed by the Opera House Board of Trustees, is also thought to relate to other issues such as his manner of communicating with staff and board members. When the Herald asked board chairman Kim Williams if the trustees had specifically discussed renewing Gillespie's contract, he replied, "Any discussion between me and other members of the trust is private."

Gillespie, a 50-year-old Irishman, was appointed in 2002 with the backing of then-Sydney Opera House Trust chairman Joe Skrzynski.

The Sydney Opera House board of trustees — which will shortly reveal the details of the A$500 million overhaul of the building being overseen by original architect Jêªrn Utzon and his son and partner Jan — will begin searching for a successor immediately.