(Reuters) - Scottish Mortgage Investment Trust (SMT), UK’s largest investment trust, said on Friday joint portfolio manager James Anderson would be stepping down in April 2022 after more than two decades with the firm. The move comes as Swedish investment firm Kinnevik , which counts Sweden’s wealthy Stenbeck family as a shareholder, proposed on Friday to make Anderson, one of UK’s most successful fund managers, its new chairman. Anderson was responsible for SMT’s investments in private companies, which was “one of the trust’s most important strategic initiatives to date”, Chairman Fiona McBain said in a statement. Shares of the FTSE-100 firm were down about 2% at 1,132 pence by 1030 GMT. The news could cause worry to investors who made “fantastic returns” over the years, said Ryan Hughes, AJ Bell’s head of active portfolios, adding that Anderson delivered 1,700% in returns since being appointed to SMT. SMT, one of asset manager Baillie Gifford’s flagship trusts, has 17 billion pounds ($23.68 billion) in net assets and boasts of having interests in companies including Tesla, Amazon and Delivery Hero. Fellow partner at SMT, Tom Slater, will continue as lead portfolio manager of the 112-year old company, when Anderson retires. Lawrence Burns, also a partner at Baillie Gifford, will become deputy portfolio manager, SMT said. Anderson will also retire as partner from Baillie Gifford, SMT said. ($1 = 0.7178 pounds)