Duncan Hendry has cited the demands of the job for his decision to step aside, pointing out he would be 72 if he decided to stay on until the planned reopening of the theatre in 2023.
Mr Hendry, who also runs the Festival Theatre, will hand over the reins of the 112-year-old venue next summer, more than two years before the £25 million project is due to start.
He has also announced his departure before final costings and designs are in place for the long-awaited overhaul.
It is the second major blow for the King’s development in the space of a few weeks after a bid for almost £5m of lottery funding was rejected.
Mr Hendry said he hoped to still be involved in the King’s campaign, which has an £11m funding gap to fill. The project involves the creation of a new street level cafe-bar and a rooftop hospitality space. It is hoped a new stage will help attract world-class opera and drama productions.
Mr Hendry insisted the project was in “a good place,” after the fundraising campaign launch, agreeing £4m worth of support and a loan agreement with the city council, and unveiling the first image of the revamped venue, which will close for two years while work is carried out.
Mr Hendry, chief executive of the Capital Theatres Trust, has overeen a doubling of turnover to £14m. Audiences have risen to 430,000 after the Festival Theatre secured National Theatre shows like The War Horse and Macbeth, as well as the Cameron Mackintosh musicals like Mary Poppins and Miss Saigon.
Mr Hendry said: “The King’s was in a pretty poor state when I started. I inherited the first phase of a refurbishment, but that was really just about getting it wind and watertight, and installing new seating.
“We spent a lot of time looking at what needed to be done to make the King’s as it should be. It’ll be another five years before the project is completed, by which time I will be in my early seventies.
“It’s an exhausting and demanding job, which probably needs someone with renewed energy to see it through to the end. It can be a 60 hour week job and the King’s project has added another dimension to it.
“There’s never a good time to go, but we now have the design team in place, a fair chunk of the funding in place and a very good team in place who can raise the balance. It feels a natural time to step down.”