Ian Hannam, the former soldier who became one of the City's best-known advisers on big corporate takeovers, yesterday opened the first day of his appeal against the fine and censure he received alleging he used insider information to help a client.
His case is one of the biggest of its kind ever to have hit the financial district and is set to run for up to two weeks as the banker fights to clear his name.
Mr Hannam was fined £450,000 by the then-Financial Services Authority for allegedly revealing price-sensitive information about a client.
He claims he was simply trying to help flush out a takeover offer for the client, Heritage Oil & Gas, by emailing what he claimed was very general information.
The case in the Upper Tribunal in London is being closely watched by City takeover specialists as it will all essentially hang on the definition of what constitutes insider information.
The QC for the Financial Conduct Authority, Richard Boulton, defended its ruling, saying the first of the two emails in question was a "paradigm" example of insider information, while the second was more "nuanced".
Even so, he went on to say: "If it looks like a duck, walks like a duck and quacks like a duck, it's probably a duck."
However, Mr Hannam's barrister described the case as "misconceived".
In a statement, Mr Hannam said: "I was acting in the proper course of my employment as a corporate financier, pursuing a transaction on behalf of my client, Heritage Oil & Gas."
The first email said to his contact, a representative of an organisation with Kurdistan business interests: "I believe that the offer will come in in the current difficult market conditions at between 350p and 400p a share."
The second said, in reference to Heritage chief executive Tony Buckingham, that he "has just found oil and it is looking good." Heritage later that month announced an oil find.
Mr Hannam claims his departure, as a result of the allegation, from JPMorgan Cazenove cost him as much as £30m in lost bonuses and pay. The case continues.
Man behind myth
Ian Hannam revelled in his status as one of the City's best-known dealmakers. A "rainmaker", or "big swinging dick" in Square Mile parlance, the 56-year-old was dubbed "King of the Miners" and made the London Evening Standard's list of the top 1,000 most influential Londoners.
While he stitched together deals in many sectors, he is best known for the mining megamoves like the $40bn creation of BHP Billiton and the flotation of Xstrata. Formerly in the Territorial Army's version of the SAS, he grew up in Bermondsey, south-east London, and was an engineer in Nigeria and Oman before becoming a banker in 1984.