Warren Buffett’s $5bn investment in Goldman Sachs is not the billionaire’s first foray into Wall Street. What may be surprising to some long-time followers is that there was a second.

Seventeen years ago, Mr Buffett stepped in as chairman of Salomon Brothers to help the firm recover from a government-bond scandal that had threatened to destroy it. He had bought $700m in preferred shares four years earlier and remained the investment bank’s biggest investor.