She has not been a member of the company's Executive Committee, whose roughly 50 members are listed in JPMorgan's annual report and who meet quarterly.
Lake has had some experience in the last five years meeting with Wall Street securities analysts, whom she will address in future quarterly conference calls after earnings reports.
In her previous roles, she saw the financial crisis up close as JPMorgan acquired investment bank Bear Stearns and then as the U.S. housing crisis battered JPMorgan's mortgage investments.
From 2007-09, she worked in JPMorgan's investment bank as global controller in finance and business management.
Lake first met Dimon when he came to the bank in 2004. Dimon, in the company's statement, said Lake "has developed an impressive breadth of knowledge and experience in finance across both our wholesale and our consumer businesses."
Lake, a chartered accountant, managed global finance infrastructure and control functions in JPMorgan's corporate finance group from 2004 to 2007. Before that, she was a senior financial officer for the company in the United Kingdom.
She also worked for PriceWaterhouseCoopers in London and Sydney before joining JPMorgan.
Lake is a citizen of both the United States and the United Kingdom, having been born to an American mother and a British father.
Dimon took Braunstein out of his line of direct reports in July, assigning him to answer first to Matt Zames, a top mortgage markets executive whom he had just named co-chief operating officer of the company.
Dimon, in testimony before a congressional committee in Washington in June, cited Braunstein as being among top lieutenants whom he had relied upon to check the London Whale reports.
Others he cited were company risk officers. In October, former Chief Risk Officer Barry Zubrow said that he would retire at the end of the year. Another person whom Dimon cited was Ina Drew, who was head of the Chief Investment Office and who left shortly after the losses surfaced.
Besides the shakeups this year, Dimon shuffled some of his top executives at least once in each of the three previous years. He has said that he likes to rotate his top staff through different positions as part of preparing potential successors.
In June 2011, Dimon replaced retail banking chief Charlie Scharf, who has since become CEO of Visa Inc.
In June 2010, Dimon named Braunstein to be CFO after Cavanagh had held the post for six years. Cavanagh was then put in charge of JPMorgan's Treasury & Securities Services unit which handles payments and other transactions for corporations and governments.
Cavanagh's assignment changed somewhat in this year's July shuffle when Dimon said the bank would combine the treasury services business with its investment bank and that Cavanagh would become co-head of the new unit, with Pinto.
In 2009, Dimon named Jes Staley to take over the investment bank, replacing its co-chief executives Bill Winters and Steve Black. At the time, it look like Staley could become a successor to Dimon, though they are about the same age.
But in July of this year, Staley was moved out of that executive role to become chairman of the combined corporate and investment bank.
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