Bill Ackman just made his biggest ever investment in another hedge fund manager

Billionaire activist investor Bill Ackman told the Wall Street Journal that he's committed the largest amount of money that he's ever allocated to another hedge fund.

Ackman, who runs $18 billion Pershing Square Capital and was the best performing hedge fund manager in 2014, has invested an undisclosed sum in 38-year-old Phi Hilal's new fund Clearfield Capital Management.

Phil Hilal is the younger brother of Pershing Square Capital partner and Ackman's college friend, Paul Hilal. Ackman told Bloomberg News last fall that Phil Hilal was someone to watch.

Last year, at Ackman's Harbor Investment Conference, Phil Hilal knocked it out of the park with his two investment ideas- Energy Transfer Equity (up 40.47%) and Northstar Realty (up 51.98%).

Phil Hilal previously worked at Kingdon Capital Management, Davidson Kempner Capital Management and Goldman Sachs. He graduated with a bachelor's in economics from Yale. He received his MBA from Harvard.

Clearfield Capital Management is expected to debut in the second quarter of this year. Reuters reported earlier that Clearfield will be a long/short equity and event-driven fund.