IAN Hannam, one of the UK's most senior investment bankers and a long-term ally of Aberdeen Asset Management's chief executive Martin Gilbert, has resigned after being fined £450,000 by the City regulator.

Mr Hannam, chairman of capital markets at JP Morgan Cazenove, fell foul of market abuse rules after the Financial Services Authority found he had disclosed two pieces of information on Heritage Oil to a potential client.

He is appealing against the decision.

Mr Hannam began his career with housebuilder Taylor Woodrow before moving into banking in the 1980s with Salomon Brothers in New York.

In 1992 he moved to Scottish banking house Robert Fleming, which was bought by Chase Manhattan in 2000 and through various mergers became JPMorgan Cazenove.

He is a former member of the territorial special air services with links to powerful figures across the globe, including US generals.

Mr Hannam has long been an adviser to Mr Gilbert, including on Aberdeen's 2008 deal with Mitsubishi UFJ Trust and Banking Corporations, which saw the Japanese institution take a 17.6% stake in the fund manager.He was also involved when Aberdeen-based bus and rail operator FirstGroup, chaired by Mr Gilbert, bought US company Laidlaw in 2007.

Mr Hannam's connections with Mr Gilbert stretch back to the late 1990s when JPMorgan advised on a deal between Aberdeen and Scottish Provident.

The two are also reported to both be investors in literary agency PFD.

There is no suggestion that there was anything improper in any of Mr Hannam's dealings with Mr Gilbert.

Tracey McDermott, acting FSA director of enforcement and financial crime, said: "Inside information is extremely valuable and must be handled with care to ensure that it is properly controlled."

Mr Hannam said: "I am appealing a decision notice issued by the FSA and have consequently decided to resign from JPMorgan."