Square Mile Investment Research and Consulting director Nigel Whittingham is to leave the firm at the end of the year.
He founded Square Mile in September 2013 alongside fellow OBSR founder Richard Romer-Lee but has now decided top leave due to family reasons.
Whittingham will return to South Africa in early 2015 but remain as a shareholder in Square Mile.
Co-founder and director Mark James will assume responsibility for the distribution side of the business.
A Square Mile spokeswoman says: “Nigel has played an invaluable and integral role in the founding and development of Square Mile and will continue to do so. All key clients and stakeholders in the business are aware of this development and are sympathetic to Nigel’s decision.”