Four years ago, Kirkland & Ellis celebrated its 100th anniversary by issuing a glossy coffee-table book chronicling the firm’s history. The book ended with a stiffly posed picture of 18 current and former members of Kirkland’s "firm committee," as the executive committee was then called.

The 17 men and one woman projected various forms of lawyerly reserve—except for one. Jeffrey Hammes—who stands out with his beaming smile, thick head of brushed-back hair, and overall expression of exuberance—looks as if he might have wandered in from a convention of television news anchors.