Brett Williams has stepped down as chief executive of Cofunds with immediate effect.
Cofunds says Williams played an important role in helping the business break through the GBP25bn assets under administration barrier.
While Cofunds looks to recruit a permanent replacement, Charlie Eppinger (pictured) will be returning to the role of chief executive.
Current board member Simon Davies, chairman of Threadneedle, takes over from Eppinger as Cofunds chairman.
Eppinger says: "Cofunds is a great company and has a strong management team already in place. The shareholders are keen to harness that strength and accelerate the pace of growth in the business to match the changes in the industry as a whole. The board recognises the need for continual investment and a real focus on serving our customers. We are committed to the success of the business and its continued independence.”