Big law enjoys a long life. For an illustration, examine “The Partners: Inside America’s Most Powerful Law Firms”, by James Stewart, published four decades ago. With a few exceptions, the book’s starring firms remain in excellent health. Cravath, Swaine & Moore, Sullivan & Cromwell and Kirkland & Ellis are still some of Wall Street’s busiest limousine-chasers. Less fortunate firms have fizzled out, rather than blown up. One shop, Donovan, Leisure, Newton & Irvine, closed in 1998. Another, Shearman & Sterling, has announced a merger with a British rival.

Mr Stewart’s book gave only a walk-on role to Wachtell, Lipton, Rosen & Katz. The same omission would be unthinkable today. Set up in 1965 by graduates of New York University, Wachtell is America’s pre-eminent boardroom adviser. Bosses tapped the firm to counsel on transactions worth $100bn in the first half of this year, and paid handsomely for the privilege. According to American Lawyer, an industry journal, last year Wachtell’s partners earned $7.3m apiece, bested only slightly by Kirkland & Ellis, a Chicago outfit which fills its boots advising on private-equity deals. Measured by profits per lawyer, Wachtell and its dealmakers, who include fewer junior staff (“associates”) for each of its senior ones (“partners”), look nearly twice as productive as the next best firm.