Tuesday September 12 2017, Bell Pottinger came crashing down after its latest effort, in South Africa, spiraled into disaster. The firm was forced to appoint administrators for its British operations as clients, employees and a major shareholder cut their ties to the firm. Bell Pottinger’s swift downfall sent shudders through the public relations industry and raised questions about the increasingly combative tactics used by those who engage in what critics call “reputation laundering.” Britain’s Public Relations and Communications Association expelled Bell Pottinger from its ranks, making it the first big company to be forced from the group. James Henderson, Bell Pottinger’s chief executive, resigned. Clients including the British bank HSBC and the luxury firm Richemont dropped the firm, its reputation as soiled as those of some of the controversial figures it advised. Timothy Bell, a London political and social operator who helped Margaret Thatcher, the former British prime minister, start her political career, was a founder of Bell Pottinger in 1998. The firm counted Airbus and Coca-Cola as clients, but it also advised President F.W. de Klerk of apartheid-era South Africa on how to run against Nelson Mandela, and helped a foundation backed by supporters of Gen. Augusto Pinochet, the former dictator of Chile, fight his detention by Britain for human rights violations. When the South African track star Oscar Pistorius stood trial for the brutal killing of his girlfriend, he hired Bell Pottinger, an aggressive British public relations firm, to try to smooth his tattered reputation. President Bashar al-Assad of Syria and his wife turned to the firm for help in recasting their image. So did Aleksandr G. Lukashenko, the dictator of Belarus. Bell Pottinger appeared to test the limits of its approach in South Africa last year when it was hired by Oakbay Capital, a holding company run by the Gupta brothers, members of a powerful Indian family with widespread business interests in South Africa.