The official line says Paul Phenix's nine-year stint as executive director of compliance at the stock exchange ended because of his desire for a new start at the Australian Stock Exchange.
On the face of things, he left mainly because he wanted a fresh challenge, as well as for health and family reasons.
However, sources said yesterday there were other behind-the-scenes factors that could have influenced his decision to leave.
One prominent market figure said Mr Phenix had 'a hide like a rhinoceros', but some of the complex and difficult issues of the compliance division 'can't help but get to you eventually'.
In particular, differences of opinion with the Securities and Futures Commission (SFC) over specific policies, as well as political factors at the exchange, have been cited as possible reasons that contributed to his decision.
Mr Phenix is known to have taken strong position on issues of deregulation and short-selling which did not always coincide with those of senior SFC officials.