Sainsbury's boss Justin King to step down in July 29 January 2014 Last updated at 09:20 Sainsbury's has announced that chief executive Justin King is to leave the supermarket chain in July. He will have been at the helm of the company for 10 years. Mike Coupe, Sainsbury's group commercial director, will succeed him as chief executive, the company said. Sainsbury's chairman David Tyler said Mr King was "a truly exceptional leader who has reshaped Sainsbury's during his 10 years as CEO. He leaves a lasting legacy.