In 1985, the Coca-Cola company changed the formula and taste of its flagship product, a universally successful drink whose name was almost synonymous with soft drinks. The new drink was called New Coke.

New Coke was introduced on April 23, 1985, with the slogan 'The Best Just Got Better," and production of the original formulation ended that same week.

Coke's over-all market share had been shrinking for decades, from 60% just after World War II to under 24% in 1983.

To preserve secrecy during pre-marketing taste tests, Coca-Cola marketers never asked the focus groups, "How about if this product replaced Coke?"

The product was launched after even Coca-Cola's own product testers discovered that people prefer the sweeter taste of Pepsi.

At an July 11, 1985 press conference, two Coca-Cola executives announced the return of the original formula. "We have heard you," said Roberto Goizueta, then Chairman of Coca-Cola.

Donald Keough, President and Chief Operating Officer, said:

There is a twist to this story which will please every humanist and will probably keep Harvard professors puzzled for years. The simple fact is that all the time and money and skill poured into consumer research on the new Coca-Cola could not measure or reveal the deep and abiding emotional attachment to original Coca-Cola felt by so many people.

At first it was a marketing and public relations debacle. The public were unhappy with the new taste, and even more unhappy that they were no longer able to obtain the original product, and so the company had to backtrack and return to the older formula. However, when they went back to the original formula - now renamed Classic Coke/Coca Cola Classic - demand for the classic taste grew to a greater extent than before New Coke, propelling Coca-Cola to continue its market lead over rival Pepsi. Therefore, the situation became an unintentional success for Coca-Cola.

New Coke was only sold in North America - the original formula continued to be sold in the rest of the world, although had the new version been a success it would presumably have been introduced worldwide.

• Barbara Mikkelson's brief guide to the lucky fiasco.

this article needs dates - when the new product was withdrawn.