Mystery surrounds the sudden, unexplained departure of Prison Service HR director Gareth Hadley last week.
Hadley resigned last Monday (13 November) after seven years in the high-profile post - and cleared his desk the same day.
It was reported that he quit after a complaint from a male member of staff about inappropriate behaviour.
Hadley admitted that an internal complaint had been made about him, but denied that this was the reason for him leaving.
But senior union officials have claimed the complaint was a "red herring" and that Hadley had resigned "for other reasons".
Hadley told Personnel Today: "It was time to move on. I have delivered significant changes and the HR service is now fit for purpose. I'm proud of what I've delivered and have decided to look for new challenges."
However, a Prison Officers Association (POA) source said: "Prison officers will be ecstatic Hadley has gone. He was an impediment to the improvement of industrial relations in England and Wales."
The union has been involved in a long-running dispute with the Prison Service over pay. "One element of the dispute has been removed with the resignation of Gareth Hadley," said the source.
The Home Office is remaining tight-lipped on the bizarre events. "We have nothing to say about his departure other than that he resigned on Monday," said a spokeswoman.
Hadley joined the service after years in the rail industry, and worked with director-general Phil Wheatley on a wide-ranging programme of reform. He is credited with ushering in a new breed of governor, changing working practices and modernising the HR function.
Hadley has endured a difficult relationship with the POA in recent times. In August, union accusations about the independence of the service's pay review body led to the first-ever vote for industrial action.