King left the over 1,230 store British retailer at the conclusion of its annual shareholders meeting in central London and was succeeded by commercial director Mike Coupe; a promotion that was announced in January.

"I'm sure of one thing, Justin's departure doesn't mean the end of this success story," said chairman David Tyler.

He paid tribute to King, calling him a "guiding light to all of us," prompting a partial standing ovation from a packed room of, mainly elderly, private investors.

King joined as CEO in March 2004 and in his 10 years transformed the 145-year-old group's fortunes, delivering over 10 billion pounds ($17 billion) in incremental sales, a near-tripling in earnings and total shareholder return (TSR) of 85 percent.

But he departs with Sainsbury's - in common with its big rivals, market leader Tesco, Wal-Mart's Asda and Morrisons - battling the lowest growth in the sector for a decade and the two pronged challenge of discount grocers Aldi [ALDIEI.UL] and Lidl [LIDUK.UL] and upmarket players such as Waitrose [JLP.UL].

Sainsbury's run of 36 straight quarters of like-for-like sales growth under King came to an end in March and it has since posted another quarterly fall.

Tyler said the board was confident Sainsbury's differentiated offer would see it emerge as a winner. That includes a focus on own-brand products, online and convenience stores, as well as expansion into non-food items and financial services.

"I know I leave the business in safe hands," said King, 53, without giving any clues on what he plans to do next.

He has said he wants another big job, though a "non-compete" deal rules him out of taking a role with any rival grocery chain for 12 months.

"Mr King has done a fantastic job here .... Is there any chance Mr King could rescue Marks & Spencer?," asked private shareholder George Conway.

Coupe, as CEO designate, has already made his mark, fronting last month's move by Sainsbury's to team-up with Denmark's Dansk Supermarked to bring the Netto brand back to the UK and take on the fast-growing German discount chains at their own game.

(Reporting by James Davey; Editing by Mark Potter)