Marks & Spencer's new boss today left his post as chief executive of supermarket Morrisons - two months earlier than expected.
Marc Bolland was due to step down at the end of January, ahead of taking on the top job at M&S.
But Morrisons said he would instead "relinquish" CEO duties today.
It is unclear if he will join M&S early, with a spokeswoman for Morrisons saying a start date was "still under discussion".
Morrisons said: "Trading arrangements for Christmas are progressing smoothly and the senior management is now focusing on plans and operations for the new year.
"It was therefore agreed at a scheduled board meeting yesterday that it would be appropriate for Marc Bolland to relinquish his operational responsibilities with effect from today."
Mr Bolland had three executive directors reporting directly to him and they will run the group until a replacement is appointed, with chairman Sir Ian Gibson leading the board.
Sir Ian added: "Morrisons has a strong and capable senior management team which will continue to operate the business. We are well placed for a successful Christmas period and a strong end to our current financial year."
Mr Bolland's appointment at the helm of M&S was announced last month in what was seen as a blow for Morrisons.
But it was hailed a coup for its rival and the end to a lengthy search for a successor to Sir Stuart Rose, who held the dual chief executive and chairman role.
Mr Bolland joined Morrisons in 2006 as chief executive and has transformed the once-ailing chain into the fastest growing of the big four grocers.
The 50-year-old Dutchman has helped the supermarket outperform the wider sector in recent months, with third-quarter figures posted in mid-November revealing a 4.3% hike in sales.
Morrisons's finance director Richard Pennycook has already indicated he would think about putting himself forward to replace Mr Bolland, but said it was too early to say for certain.
Today's news comes at a critical time for the retail industry, with the sector in full flow for the Christmas selling season.
Food chains have been stepping up a price war to tempt in shoppers, with Morrisons battling against stiff competition from its bigger three rivals as well as the likes of the Co-operative, which recently waded in with swingeing price cuts.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies