"Buckaneering" Ian Hannam was one of the most influential bankers of his generation, but has been slammed with a £450,000 fine by the FSA.
Hannam resigned from his post as global chairman of equity capital markets for JP Morgan on Tuesday.
The FSA said the fine was intended to punish Hannam for passing on inside information about Heritage Oil to another contact. They said it would also act as a deterrent to others.
Many former collegues have rushed to defend Hannam, saying he was an outstanding banker who changed the face of the FTSE 100. David Davis, a prominent Tory backbencher, said that the FSA action was "unbelievable", and "un-british".
After studying engineering at Imperial College, Hannam joined the Territorial Special Air Service, serving for 21 years. He then became an engineer at Taylor Woodrow, later studying for an MBA and moving into banking.
At JP Morgan he made his reputation as a dealmaker, specialising in mining. He had a hands-on approach which distinguished him from his competitors - but his unconventionality might have lead to his downfall.
On former college told the FT: “I suspect that people like Ian make the deskbound civil servant wallah feel a bit uneasy. He’s out of their comfort zone.”