Millett, aged 61, will leave his role as Group CEO of Mace Group and Mace Construct but will continue to sit on the board of newly-independent Mace Consult as a non executive director while also exploring fresh opportunities.

His departure follows the completion of Mace’s demerger of its Consult business, leaving Mace Construct to push ahead as a simpler, more focused construction operation.

Millett is remaining in post until year-end to support the transition and help shape the contractor’s new identity and strategy.

Executive chair Mark Reynolds will take a more active role in Mace Construct during the handover, working with the executive committee and construction leadership team.

It is understood Mace will now review future leadership strategy and succession before deciding on details of a leadership search in the coming weeks.

Millett joined Mace in 2008 through the CLM Delivery Partner joint venture and went on to play a leading role in delivery of the London 2012 Olympic and Paralympic Games.

He was part of the 2013 management buyout and later became chief executive of Mace Consult in 2020, leading its global growth.

He was appointed deputy group chief executive in 2024 before taking the top job in January 2025.

Reynolds said: “Jason has played a crucial role in the success of the business over the past 18 years and, during his tenure as chief executive, has provided exceptional leadership across both our Consult and Construct teams.

“Over the coming months, Jason and I will work closely together as he transitions out of the business, and the Board shapes its future leadership plans for Mace Construct as we develop our new identity and strategy.”

Millett said: “Following the successful separation of Mace Consult, this felt like a natural moment to reflect on what comes next.

“I believe Mace Construct has a strong sense of direction and a significant opportunity ahead as a simpler and more focused business.”