Sir William Felix Browder is an American-born British financier who co-founded Hermitage Capital Management and served as its CEO. He is the investment advisor to the Hermitage Fund, which became the largest foreign portfolio investor in Russia. The fund was established in partnership with Republic National Bank with $25 million in seed capital and eventually grew to $4.5 billion in assets under management. Browder's investment approach centered on shareholder rights activism, through which he challenged major Russian corporations including Gazprom, Surgutneftegaz, Unified Energy Systems, and Sidanco. His work in this area proved successful early on, with the Hermitage Fund achieving a 238% return in 1997, making it the best-performing fund in the world that year. Browder's activities in Russia led to significant consequences. On November 13, 2005, he was refused entry to Russia, deported to the United Kingdom, and officially declared a threat to Russian national security. Following these events, he became known as a political activist in addition to his role in finance.