NHS Yorkshire and the Humber chief executive Margaret Edwards left her post suddenly last week to take on a new role driving efficiency across the NHS.
As revealed on hsj.co.uk last week, Ms Edwards is to become national director of productivity and efficiency at a newly created NHS national productivity unit, following a short break.
NHS East Midlands chief executive Barbara Hakin stepped in last Friday to run Yorkshire and the Humber on an interim basis, in addition to her existing role.
Ms Hakin told HSJ she had only found out about the new job "late last week", but knew the patch well, having been a primary care trust chief executive in the region.
She said her first step would be "as all good incoming people [would], to have a thorough assessment of the situation".
Ms Edwards did not attend the strategic health authority’s board meeting on 3 March, three days before her departure was formally announced.
In a statement sent to all SHA employees on Friday, she thanked staff for their support during her three years in the post.
She said she was "delighted" to have been asked by NHS chief executive David Nicholson to lead work on increasing productivity and efficiency nationally.
Senior figures expect the national productivity unit to consolidate work around how efficiency savings can be translated into policy action, potentially even influencing the direction of the tariff and the operating framework.
One source said: "Given that we've got to make pretty swingeing efficiencies and get decent productivity gains, it will be quite helpful at some levels to get a focus nationally."
Mr Nicholson said the NHS must "start now to prepare for the leaner times that inevitably lie ahead".
The Department of Health would not say how many staff the unit will have, what its budget and duties will be, how long it will run for or what its relationship to SHAs and PCTs will be. But a spokeswoman said Ms Edwards, who has an economics degree and an MBA, would be setting it up "from scratch".
It will be hosted by NHS London. Director general of NHS finance, performance and operations David Flory will be its DH "sponsor".
In a statement, NHS Yorkshire and the Humber chair Kathryn Riddle thanked Ms Edwards for her contribution. She said: "The board hope she will continue to bring her youthful energy, vision and experience to her new role."
HSJ has been told of tensions over the way the SHA had been run. One senior manager in the region said it was felt there was too much emphasis on "bottom line performance" at the expense of strategy. "I think there’s been a real schism in that health authority," he said.
Ms Edwards was unavailable for comment.