Nelson Peltz, the billionaire activist investor well-known for revamping Cadburys and Wendy's, has become the largest shareholder in US asset manager Legg Mason, marking his first substantial investment in a large financial company.

Regulatory filings this week showed that Peltz's hedge fund Trian bought over two million shares in Legg Mason on Monday, bringing its total stake to 9,048,044 shares; equivalent to 5.6% of the company. Another US asset manager, Dodge & Cox, is now the second largest shareholder, with a 5.5% stake.