American hedge-fund manager. Ackman runs Pershing Square, whose London-listed Pershing Square Holdings has generated annualised investor returns of 16.2% after fees from its predecessor's 2004 debut through end-2025—against 10.7% for the S&P 500. In April 2026 he raised $5bn for Pershing Square USA, the largest "closed-end" fund ever launched, listed on the New York Stock Exchange. Mr Ackman calls it an attempt to build a modern-day Berkshire Hathaway.
He missed an invaluable opportunity to hold his tongue.