Barbara Judge, a high-flying American-British lawyer, banker and entrepreneur who broke the glass ceiling of male dominance at regulatory agencies and other influential institutions in Washington, Hong Kong and London, died on Monday August 31 2020 at her home in London. She was 73. Her personal assistant, Susan Cavanagh, said the cause was pancreatic cancer. As the youngest person — and only the second woman — to become a commissioner of the Securities and Exchange Commission, appointed in 1980 by President Jimmy Carter, and later as the first female chair of Britain’s Atomic Energy Agency, In her public life she championed the advancement of women in business, and she set her own example: She was, at various times, the first female executive director at a British merchant bank and the head of London’s clubby Institute of Directors. Such was the breadth of her interests that she was sometimes criticized by adversaries for assuming too many roles — notably when she served as a board member responsible for safety and other issues at Massey Energy, a United States coal concern, at the time of a disaster that killed 29 miners in 2010. Ms. Judge — who took the title Lady Judge, as protocol permitted, after her marriage in 2002 to Sir Paul Judge — also drew some criticism from groups advocating a greater role for women in business when she gave a speech in 2016 in which she said she opposed long maternity leaves because such “breaks are bad for women.” Nonetheless, she later took nine months off work to help her son meet the challenges of dyslexia by nurturing his education. He graduated with honors from the University of Pennsylvania. Ms. Judge was also known for her roles in higher education and the arts. She was associated with an array of business schools in Britain and the United States, including the Wharton School of the University of Pennsylvania. But her stellar trajectory splintered in 2018, when she was forced to resign as chair of the Institute of Directors, founded in 1903 to promote the interests of senior managers. Critics accused her of sexism, racism and bullying — charges she said she “strongly” refuted. She and her allies at the 30,000-member institute, whose colonnaded headquarters are on Pall Mall, an upmarket London thoroughfare lined with exclusive male-dominated private clubs, argued that she had been the victim of a conspiratorial maneuver to entrap her. One of the institute’s most senior figures, for instance, had covertly recorded his conversations with her to bolster the accusations against her. Details of those conversations, and of a draft report of a lawyer’s investigation into the episode, were leaked to British newspapers, triggering her decision to quit. The scandal was particularly damaging in light of both her reputation and that of the institute. Ken Olisa, the institute’s deputy chair and one of Britain’s best-known Black entrepreneurs, resigned in support of her on the same day she did. Barbara Suzanne Singer was born in Manhattan on Dec. 28, 1946. Her mother, Marcia, was associate dean of students at New York Institute of Technology. Her father, Jules, was a businessman. She was the eldest of three children. When she was 19 she married a fellow student at New York University School of Law, Theodore J. Kozloff. They divorced in 1975. In 1979 she married Allen L. Thomas, who like her was a lawyer; they had a son, Lloyd, in 1983. The marriage ended in 2001. In 2002 she married Paul Judge, a British entrepreneur, philanthropist and fund-raiser for the Conservative Party. He died in 2017. In addition to her son, she is survived by her mother; her sister, Nancy Singer; her brother, Michael; and a granddaughter. She qualified as a lawyer in 1969 and worked as a corporate lawyer in the city before joining the S.E.C. In 1983 she and her husband moved to Hong Kong, where she became the first female director of a British investment bank, Samuel Montagu. She later joined Bankers Trust in New York. As a director of Rupert Murdoch’s News International, she moved to Britain in 1994. She went on to head an array of British regulatory bodies, including the Atomic Energy Agency; Britain’s fraud prevention service, Cifas (the Credit Industry Fraud Avoidance System); and the Pension Protection Fund.