Andrew Green will step down as lead portfolio manager of the GAM UK Diversified and GAM Global Diversified funds after 34 years.
From 1 January 2018 Chris Morrison and Adrian Gosden will co-manage the GAM UK Diversified fund while Ali Miremadi will manage the GAM Global Diversified fund.
Mr Green will continue to manage a few select mandates and will provide advice and support to GAM equity teams in the new role of director of global equities strategy.
He joined GAM in 1983 when it was founded by Gilbert de Botton.
Mr Green said: “Gilbert’s entrepreneurial spirit and innovative approach to meeting clients’ needs through active management are still at the core of GAM’s DNA.
“True to these values, Adrian, Chris and Ali are passionate about delivering meaningful returns for clients, and I wish them every success in the future.”
Mr Gosden joined GAM in September 2017 with 20 years of investment experience while Mr Morrison has been working as an investment manager supporting Mr Green for the past seven years.
Mr Miremadi joined GAM in 2016 from THS Partners, a global equity investment firm that has been a long standing sub-adviser to the GAM Star Worldwide Equity fund.
Alexander Friedman, chief executive of GAM, said: “Throughout his professional life spanning nearly 50 years in finance, Andrew has gained legendary status in the industry.
“He is universally lauded as an outstanding and disciplined investor, a status underscored by numerous awards and accolades throughout his career.
“His investment philosophy has helped to create GAM’s conviction-led culture, forming one of the core principles on which our brand is built today.”
Martin Dodd, a financial adviser at Wolverhampton-based Midlands Investment Agency, said he would not necessarily sell down on a fund if the manager left but said he would place it under more scrutiny.
He said: "My view is that most long-standing managers will have a pretty solid team around them and unless they have taken their entire team with them, if it has been a strongly performing fund it will probably continue to be one.
"If you look at Invesco Perpetual that has been the case after Neil Woodford left."