Michael Spencer, the billionaire behind one of the world’s biggest financial brokerage fortunes, has lost the head of his personal investment firm appointed just months ago.

Ion Bogdaneris became chief executive officer of IPGL, the NEX Group Plc founder’s family office, in February but stepped down from the firm late July, according to UK registry filings.

A spokesman for London-based IPGL confirmed Bogdaneris’s departure and said the former American International Group Inc. executive left the family office for personal reasons.

Bogdaneris didn’t immediately respond to a request for comment.

His move leaves a gap at the helm of IPGL, which has £1.1 billion ($1.4 billion) in net assets according to the firm’s latest filings, and oversees stakes in more than three-dozen businesses, including UK wine-maker Chapel Down Group Plc, pool betting operator The Tote and cybersecurity firm Glasswall.

Spencer Fortune

Bogdaneris, 65, was appointed by IPGL to replace Samantha Wren, a former NEX executive who led the investment firm since 2019. He previously headed AIG’s European alternative-investments business as well as a private investment firm for Jacob Rothschild. His most recent role prior to joining IPGL was helping run the family office of Lululemon Athletica Inc. founder Chip Wilson.

Read more: Billionaire Michael Spencer Taps Ex-AIG Boss to Run His Fortune

Spencer, a 68-year-old former Conservative Party treasurer, originally made his fortune through ICAP Plc, NEX’s predecessor company, a business he founded in 1986. The firm grew to become the world’s biggest broker of deals between banks and turned Spencer into one of the City of London’s most prominent figures.

Through IPGL, Spencer has diversified his fortune into real estate, wine and wealth management. In recent years, it invested in German insurtech platform Hepster and British e-sports franchise EXCEL Esports, while it also holds a stake in CME Group Inc. that’s below reporting thresholds.