LONDON — If an autopsy could have been performed on Bell Pottinger, Britain’s most audacious public relations firm, the cause of death may have been summarized as “acute embarrassment.”

This is ironic because Bell Pottinger always seemed defiantly beyond shame. During its 30 years in the upper echelons of Britain’s spin doctoring game, it sought to polish the image of dictators (Alexander Lukashenko of Belarus), repressive regimes (Bahrain and Egypt, to name two) and celebrities accused of despicable crimes (the Olympic runner Oscar Pistorius after he was charged with murder).

But in early 2016, Bell Pottinger signed a client that ultimately buried it in disgrace. The company worked for the Guptas, three brothers from India who built a sprawling, multibillion-dollar corporate empire in South Africa. Ajay, Tony and Atul Gupta had earned fantastic sums leveraging their friendship with President Jacob G. Zuma. By bullying officials and bending regulations to their will, they secured contracts in fields as varied as armaments, mining and railways. They offered ministerial jobs to politicians of their choosing. The Guptas and Mr. Zuma were so intertwined that critics had taken to referring to the “Zupta regime.”

As the power of the Guptas and their holding company, Oakbay Investments, gained attention, the family wanted the public relations equivalent of a stun grenade — a distraction that would draw attention away from them and onto their many enemies.