The vast investigation into insider trading on Wall Street that culminated this week in Raj Rajaratnam going on trial in New York accused of securities fraud was always likely to ensnare a large institution – perhaps a big hedge fund or a Wall Street bank. No one, however, expected the institution in question to be McKinsey & Co.

It was bad enough for the blue-chip management consultancy when Anil Kumar, one of its partners, admitted to supplying Mr Rajaratnam with inside information in return for bribes (Mr Rajaratnam denies all charges). But the Securities and Exchange Commission’s claim last week that Rajat Gupta, who was the head of McKinsey between 1994 and 2003, passed on tips as a board member of Goldman Sachs and Procter & Gamble, is a heavy blow.

Mr Gupta insists he did nothing wrong, although he has resigned his directorships of P&G and AMR, American Airlines’ parent company, having already stepped down from Goldman. But the very fact that a former leader’s conduct has been questioned has shaken McKinsey’s 1,300 partners. “Anger, disbelief, shock, sadness and outrage,” is how one describes the mood.