Mr Lee had supported Mr Glass in the running of the fund since November 2013.
City Financial said it has begun reviewing the “future viability” of the fund following Mr Glass’s departure, leaving its future in some doubt.
According to an update on City Financial’s website, the fund manager has left to “pursue other opportunities outside of the fund management industry”.
The fund, which is now just £16.5m in size, was renamed the Defensive Global Bond fund in September 2013, having been launched as the Strategic Global Bond fund in 2006.
In the past 12 months to November 19, the fund has lost 2.2 per cent, compared to the IA Global Bonds sector which lost an average 3.2 per cent, FE Analytics shows.