Samwell-Smith joined Initial in 1997 and was upped to creative director in 2006, and then managing director in 2013.
He is best known for overseeing 15 seasons of Big Brother in the UK across its broadcasters Channel 4, and latterly Channel 5, and both to considerable ratings success.
In other changes at the prodco, which also produces shows including Total Wipeout and Dating in the Dark, Sandra Smith has been upped from head of production to director of production.
Samwell-Smith said he will embark on ‘new adventures’ after a break: “I want to bow out whilst on a high,” he said. “During my time here I’ve worked on a huge range of amazing shows, with brilliant people, and I know that Initial’s tradition of creating outstanding entertainment shows will be assured under Mirella’s stewardship.”
New boss Breda said: “I’m going to miss working with Nick enormously. He leaves Initial in great shape. It’s a privilege to pick up the mantle of leading this brilliant company and our extraordinary team.”
Endemol Shine UK CEO, Richard Johnston added: “Nick was the first person I met on joining the company and I’ve seen him grow into a brilliant creative producer, and, more recently, a great leader of Initial.
“I’m understanding of his wanting to draw a line at this point though and on behalf of the Initial teams and wider group wish him the best in whatever he chooses to do next.”
Samwell-Smith’s departure the latest in a long line of changes at Endemol Shine, many of which have affected the British Endemol Shine UK arm.