Sainsbury's CEO Justin King has decided to step down in July after 10 years at the helm as the supermarket's chief executive, it has been announced.
King, who is widely credited with turning Sainsbury's into the best performing supermarket chain in Britain, will be replaced as chief executive by the group's commercial director Mike Coupe.
Over King's time as chief executive, Sainsbury's has attracted 10 million additional customers a week and has been nominated supermarket of the year six times in the last eight years at the Retail Industry Awards.
Sainsbury's has also recently started to close the gap on its supermarket rival Tesco, as it has been the only supermarket from the Big Four to increase its market share in the 12 weeks to mid-September last year.
In a statement, King said: "This was not an easy decision for me to make, and in truth it will never feel like the right time to leave a company like Sainsbury's.
"It has been a privilege to have led the Company for the past 10 years and I am incredibly proud of our achievements in that time.
"It is the 157,000 colleagues that make Sainsbury's so special and I would like to thank them for their amazing efforts over the last decade in making Sainsbury's great again. I am confident that under Mike's leadership the business will go from strength to strength."
King's departure will come as a surprise to some because as recently as last year he insisted he would be staying on at Britain's third largest grocery retailer for longer.
Speaking at a press conference last year in which Sainsbury's unveiled a 1.8% rise in sales for the year to March 2013, King said speculation about his departure was "complete fiction".
He also suggested in a television interview that he would remain chief executive of the supermarket chain for a "few more years".
King added: "I am not planning on going anywhere. I see myself staying at Sainsbury's."
Sainsbury's chairman David Tyler insisted that King was doing a "cracking job", adding: "He would have to persuade me very hard if he wants to leave at any time.”