Struggling retail giant Marks & Spencer has replaced chief executive Roger Holmes with Stuart Rose, former head of clothes store group Arcadia.
Stuart Rose is taking over the M&S top job
M&S added that chairman Luc Vandevelde, who announced his intention to resign on 10 May, was leaving immediately.
He will be replaced on an interim basis by investment banker Paul Myners.
The management clearout comes as M&S is bracing itself to fight off an anticipated takeover bid from retail tycoon Philip Green.
Mr Green said on Friday that the financing for his bid - thought to be worth up to £10bn - was "virtually in place," triggering speculation that a formal offer could come as early as this week.
BBC business editor Jeff Randall called Mr Rose's surprise appointment "a sensation".
"I cannot remember the last time a company dumped its chief executive and chairman to defend a bid that hasn't even taken place," he said.
Mr Rose, whose retail career began with a 17-year stint at M&S, is credited with engineering a dramatic turnaround at Arcadia, owner of the Top Shop and Dorothy Perkins clothing chains.
M&S, facing a renewed slide in sales after emerging from an earlier downturn in 2000/01, will be hoping that Mr Rose can put together an equally effective comeback strategy in his new role.
His main task will be to revitalise M&S' core clothing division, which suffered a surprise 2.5% dip in sales during the first three months of the year.
He is also expected to lead the store's campaign to fend off Philip Green's takeover attempt.
Mr Rose, who was head of Arcadia when it was bought out by Mr Green in September 2002, has previous experience of takeover negotiations with the billionaire retail tycoon.
The former Arcadia chief told BBC Radio Five Live he was "delighted" to be taking over at M&S.
He said his top priority would be to revitalise the company's fortunes.
"This business is not bust - this a fine business with a great heritage with 10 million customers a week coming through its stores, and which made three quarters of a billion pounds in profit last year."
"What I think has happened is that it's lost some of its glory days image. The market externally has become intensely competitive, and I think M&S has been squeezed. "
Mr Rose added that the M&S board would weigh up any takeover offer that was put to it.
"Every time you're faced with a situation like that, the board and the advisors have to meet and say under the circumstances, is this a good offer, and if that time comes, I'm sure there'll be a similar sort of meeting."