Mr Whittall began his evidence to the inquiry this morning.
It took more than a year to find a suitable safety officer, and Mr Whittall went through four different recruitment drives unsuccessfully. Eventually, Neville Rockhouse was given the role at the end of 2006.
Mr Whittall told the inquiry how roles were developed and created at the mine, from 2006 up until the time of the explosion. He had to take on different responsibilities at various times until suitable staff were found.
The mine was competing with companies in Australia and good people were difficult to find, he said.
He told the inquiry he had been chief executive for only six weeks when explosions at the West Coast mine killed 29 workers.
He had been employed with the company since 2005 in various management role.
The final witness to give evidence in this phase of the inquiry, Mr Whittall is expected to face tough questions about claims the mine compromised safety to save money.
The first phase of the inquiry focused on New Zealand's regulatory environment, and the geography, approval and development of the mine.
A series of experts told the inquiry last week that PRC had insufficient knowledge of the geology of the mine, ignored the advice of mine experts, overestimated its profitability and underestimated safety risks.
