Ackman wagers $2.2bn on Air Products stake Bill Ackman: £4.5m donation to Saïd Business School Bill Ackman, the activist US hedge fund manager, has disclosed his biggest ever investment with a $2.2bn stake in the industrial gas company, Air Products. The move points to the growing ambitions of US activist investors. With an almost 10 per cent stake in the $23bn company, the investment comes after Mr Ackman unseated the chief executive of consumer goods giant Procter & Gamble this year. Mr Ackman's $13bn hedge fund, Pershing Square, funded the purchase in part with capital raised for a standalone fund dedicated to Air Products, without disclosing to investors his intended target. The investor told CNBC on Wednesday that Air Products was a "great business that is undervalued," ending over a month of speculation. Mr Ackman said he did not intend to call for a break-up of the company, but in a regulatory filing Pershing Square left its options open. It said it would seek discussions that "may relate to governance and board composition, management, operations, business, assets, capitalisation, financial condition, strategic plans and the future of the [company]." Over the past five years, Air Products shares have risen just 11 per cent compared with a 34 per cent rise for the S&P 500. In a statement, the company defended the "proactive steps" it had taken in recent years to increase profits in a challenging economic environment and said it welcomed new investors and was looking forward to engaging with Pershing Square. The company, which supplies gases such as hydrogen and oxygen for industrial processes, installed a so-called poison pill measure last month that restricted the ability of an investor to acquire more than a 10 per stake - a tactic said to have prevented Mr Ackman from accumulating a larger holding. For Mr Ackman, the bet on Air Products comes at a testing juncture. Pershing Square has already lost "hundreds of millions" this year on a $1bn short position the fund holds against the nutritional supplements maker Herbalife, which Mr Ackman says is a pyramid scheme. It is also the second time he has formed a single stock vehicle. In 2007 Pershing took a 10 per cent stake in US retailer Target. Derivative bets on the company proved worthless, however, after Mr Ackman lost a shareholder vote and investors in the special purpose vehicle lost their entire investment. His new vehicle has purchased stock directly, according to the regulatory filling. Other investments have nevertheless paid off, and Mr Ackman remains one of the US markets" most closely followed investors. Pershing Square's flagship fund is up 8.3 per cent this year, according to a client of the firm. In early trading in New York Air Products shares traded above $109 a share, taking it to a more than 15 per cent rise over the past two weeks.