Pershing Square Holdings (ticker: PSH) is the third-largest investment trust on the London market with net assets of around £8bn. Although it traces the history of its returns back to 2004, the trust was first listed on the Euronext market in Amsterdam in 2014 before adding a London listing in 2017. Pershing Square is run by the hedge fund manager Bill Ackman, who is a big fan of the investing approach taken by Warren Buffett, and it runs a very concentrated portfolio of between 8 and 12 positions. Ackman has a history of activism, although seems to have toned that down in recent years, and he...