Whittall, who was promoted to chief executive shortly before the explosion in November, is expected to shed light on operational challenges and safety aspects.

Whittall’s promotion meant he spent less time on the ground at Pike monitoring safety as the company struggled to achieve production targets. Some believe this may have been a factor in the events that lead to the explosion.

Representatives from the NZ Department of Labour – which has also received its fair share of criticism over the tragedy – are expected to take to the witness box today.

Their answers will be keenly followed as debate rages in New Zealand about whether the Department of Labour is the right body to enforce safety standards in the mines or whether a system of independent inspectors, phased out in the 1990s, should be reinstated.

Former chief mine inspector Robin Hughes said downgrading of safety in the country’s mining legislation was a factor in the Pike River tragedy, when questioned last week at the inquiry.

Hughes said the explosion at the mine was in part a consequence of the repealing of NZ’s Coal Mines Act in 1993.

"The mines inspectorate changed from being an active and expert participant in coal mine safety to a reactive and substantially less well qualified organisation,” he told the inquiry.

“It became an ambulance at the bottom of the cliff, not a fence at the top."

From 1999 onwards the attendance of inspectors at coal mines significantly dropped and many qualified inspectors left the industry, while those that remained visited mines less frequently, he reportedly said.