Thornber passed away on 28 December. He had worked with the group since Threadneedle’s inception in 1994, joining the global equities team in 2003.
His responsibilities have been assumed by senior members of the team under the leadership of William Davies.
The $2.3bn (£1.87bn) Global Equity Income Fund, which Thornber had managed since June 2007, will be taken over by Jonathan Crown, deputy manager on the fund since 2011.
Mark Burgess, CIO EMEA and global head of equities, said: “Stephen was a talented investor, a true professional and a gentleman.
“He was a terrific influence on people across the whole firm and will be remembered by his colleagues and clients with warmth, affection and great respect.
“He has been part of our investment team from the start, and I speak on behalf of the whole firm in expressing our deep sadness at his passing. We keep Stephen and his family in our prayers at this very difficult time.”
