Abigail Johnson: The $1,600,000,000,000 woman

Abigail Johnson has moved up through the ranks of the firm founded by her grandfather (AP)

Abigail Johnson has been confirmed as the most powerful woman in the global fund management business following her promotion to president of Fidelity Financial Services. Despite the fact that she will still report to her 82-year-old father, the chairman, Edward Crosby "Ned" Johnson III, she has now been anointed to take over the running of the business which was created by her grandfather 66 years ago.

That means she has overall charge of a staggering $1.6 trillion (£1 trillion) of American and worldwide investors' savings, pensions and investments.

But that comes as no surprise in Fidelity's home city of Boston. Not only are the Johnsons one of the best known so-called Boston Brahmins, wealthy, philanthropic New Englanders, but they can trace their history directly back to Thomas Perkins, one of the first great Bostonians.

He made his fortune trading, among other things, slaves from Haiti, furs from Northern America to China and smuggling opium from Turkey into China. When he was just 12 Mr Perkins was reportedly in the crowd which heard the first Boston reading of the American Declaration of Independence.

Unlike their forebears the Johnson family are highly secretive and guard their privacy with care. On their rare forays into Bostonian society journalists hang on their every word.

As in April when the Greater Boston Chamber of Commerce held an event honouring Ned Johnson and his family as Distinguished Bostonians.

Abigail, 50, hinted at the enormous shoes she may one day have to fill, noting her father's legendary devotion to customer service. She called him "a man consumed with passion and endless energy for fixing things".

Although it was his father who started the firm in 1946, Ned Johnson was the catalyst behind the phenomenal growth of Fidelity. He joined the firm as a research analyst in 1957, moving on to portfolio manager and running the most famous Magellan Fund from 1963 until 1977 when he became chief executive of the firm.

Ned Johnson embraced new technology and new ways of doing business. He was one of the pioneers of discount broking, which made stock-market investment accessible to millions of middle-class Americans. His was the first firm to allow clients to write cheques against their investment funds. He embraced automated broking and clearing services.

Mr Johnson believed that family ownership (under slightly obscure Massachusetts Business Trust rules) allowed Fidelity to avoid short-termism and invest in long-term growth.

To this day the firm is 49 per cent owned by the family with the other 51 per cent spread among employees.

From 1966, when it managed funds worth $2.7bn, Fidelity grew to manage $75bn in 1986 to $502bn in 1996 and $1.6trn today.

But for all that time Ned Johnson kept the firm and the world guessing as to what might happen when he retired or died.

Abigail is one of three children. She was born in December 1961 and had the classic upmarket New England education at a private day school in Cambridge, Massachusetts, a degree in Art History and the obligatory MBA from Harvard.

After a brief stint with management consultants Booz Allen she joined the family firm as a mutual or unit trust manager in 1988. Since then she has moved around most parts of the firm, gradually climbing the executive pay grades.

But until now her father has ensured that there were always people between or beside her who could make it to the top slot. Even until Monday night Ronald O'Hanley, president of asset management and corporate services, was deemed her equal. Today he retains those roles but reports to her.

In the past others have been tipped to be successor to Ned. One such was Robert L Reynolds, who was chief operating officer between 2000 and 2007. He later said, only half jokingly: "I had the top job at Fidelity, but not the top job. And when I asked my parents, they wouldn't let me change my name to Johnson."

Abigail Pierrepont Johnson is as publicity shy as her father. A mother of two, she is married to Christopher Mckown, who runs healthcare information company Iora Health. They live in the upmarket Greater Boston town of Milton, which was the birthplace of President George Bush Senior.

But despite the fact that she is reckoned to be the 33rd-wealthiest person in America by Forbes magazine, with a fortune of $10.3bn, she is said to be liked and respected by Fidelity employees. Up close she is described as a smart but sober dresser with a fairly serious and reserved manner. Friends get to call her Abby.

Although she now has day-to-day running of the business it remains to be seen how much her father still makes the really big decisions. A spokeswoman pointed out that he is "not standing aside" and his power on Wall Street and in Washington appears as strong as ever. He recently was key player in defeating tighter regulation of money-market mutual funds put up by the Securities and Exchange Commission.

But fund management experts say Abigail's promotion should signal that Fidelity is prepared to make changes rather than just talk about them.

In recent times it has fallen behind mighty rivals like Blackrock and smaller lighter-footed firms like Vanguard. In the past five years investors have withdrawn $45bn.

Fidelity failed to jump on investment bandwagons like private equity, property and more recently exchange-traded funds. It has also failed to address the case that many more private investors want more direct control of where their money is invested rather than placing it all in the hands of single fund managers.

In the UK Fidelity has some 660,000 clients and runs over $214bn worth of assets but has had mixed fortunes highlighted, perhaps, by the rise and fall of star fund manager Anthony Bolton's Special Situations Fund, which became too large to manage.

"The problem that Fidelity has in the UK is big fund manager disease – once a fund manager hits a large size or runs very large funds it becomes extremely difficult to perform," says Alan Miller, founder of fund manager SCM Private.

He adds: "Their US arm seems to be run much more on old-fashioned family principles and aligning consumer interests to their own. For example in the US, many of the largest funds like the flagship Fidelity (US) Magellan fund pass back some of its economies of scale back to investors through lower fees."

It remains to be seen if New England is ready to move on from the Boston Tea Party to Abigail's Party.

Money managers: Females in funds

Katherine Garrett-Cox

Chief executive of Alliance Trust, manages £2.4bn.

Helena Morrissey

Chief executive at Newton Investment Management, manages £45bn.

Elizabeth Corley

Chief executive of Allianz Global Europe, manages £106bn.