DLA Piper's global co–CEO Nigel Knowles has orchestrated one of the most remarkable transformations in modern legal business. In his managerial career of 17 years, he has overseen no fewer than 26 mergers, acquisitions, and alliances for his firm, taking DLA from a regional U.K. outfit to a global giant in record time. DLA's revenue has grown over 3,100 percent over that period, hitting $2.44 billion in 2012. It is now the world's largest law firm by both revenue and attorney head count.

When Knowles was first elected managing partner of Dibb Lupton Broomhead, one of DLA's ancestor firms, in 1996, it was a small, regional practice in the north of England, with revenues of just £50 million ($76 million). Michael Payton, senior partner of U.K.–based Clyde & Co, remembers Dibb Lupton as a local player that was doing "tolerably well."

"If you'd said back then that those guys would become the largest firm in the world, you'd be taken off to the sanatorium," Payton adds. "The concept that a firm might have offices around the country, let alone the world, was laughable."

Not to Knowles. Recognizing that the market would consolidate, in his first postelection address to the partnership, Knowles set out an agenda for radical and rapid expansion, starting with the country's most competitive legal market: London. Within months, Knowles had sealed what at the time constituted the largest-ever U.K. law firm merger, combining with London-based Alsop Wilkinson to form Dibb Lupton Alsop (the "DLA" in DLA Piper). The move doubled the firm's revenue to around £100 million ($152 million) and gave it a foothold in the capital. At a partner retreat in 1998, Knowles revealed bigger plans: to take the firm international for the first time. His strategy was first met with "deep skepticism," says DLA's international COO, Andrew Darwin. "A lot of the partners, myself included, were saying it was too risky—but Nigel has never been afraid to lead from the front," Darwin adds. "He had the vision to recognize that the market was changing, and the leadership to then go out and do what was necessary."

In 1999 Knowles announced the launch of a broad European alliance with firms in Belgium, Italy, and Spain. Other European mergers followed, including deals in Austria and the Netherlands. But the most significant step in creating one of the first truly global law firms came in 2005, when DLA completed a three-way trans-Atlantic tie-up with American firms Piper Rudnick and Gray Cary Ware & Freidenrich.

Darwin is in no doubt as to the extent of Knowles's influence: "Without him, DLA wouldn't exist in its current form."