When Warren Gorrell became the chairman of Hogan & Hartson, in 2001, he assured the firm’s partners he wasn’t going to do anything drastic. He told them they could trust that he would never lead them into a transformational merger. The culture they had built together was too important to the firm and couldn’t be matched, he said.

Eight years later, he changed his tune—and the legal landscape. Gorrell merged Hogan & Hartson with London-based Lovells to create Hogan Lovells, a global behemoth that now boasts more than 2,500 lawyers and $2 billion in revenue, not to mention the hundreds of happy partners who benefited from his about-face.