Ross Mandell, Sky Capital’s chief executive, liked to describe himself as the “bad boy of Wall Street” – a moniker that has acquired greater resonance by allegations he “bullied” brokers at his firm into helping him operate a $140m investment fraud.

But even before the criminal and civil complaints lodged against him on Wednesday, the 52-year-old New Yorker had a history of flirting with the dark side of the Street.