His wealthy customers liked what was then the luxury of a hot chocolate drink from cocoa. As time went on, he found himself selling more chocolate than anything else. By 1847, Cadbury had enlisted his brother Benjamin and set up the Cadbury company to make cocoa-based products. Business boomed as the cost of cocoa came down and chocolate reached the working classes.
In 1853, the brothers received a royal warrant to supply Queen Victoria with chocolate. The company was kept in the family when John's sons Richard and George took control on his retirement in 1861. It was the second generation of Cadbury brothers who would create the modern Cadbury company.
By the beginning of the 20th century, Bournville, the Birmingham factory where Cadbury was based, employed more than 2500 people.
Dairy Milk was created in 1905, with full-cream condensed milk giving a creamier taste. This product would shape both the Cadbury business and the brand over the next century. Diary Milk was the base chocolate for development of Cadbury's Chocolate Buttons, Milk Tray, Fruit & Nut and Whole Nut.The design of Dairy Milk's wrapping would evolve over the next few years until, in 1920, the deep purple associated with Cadbury's was introduced.
In 1928, a press and poster campaign featured the line 'A glass and a half of full-cream milk in every half pound' for its Dairy Milk brand.
The image remains a core part of Cadbury's message today.
Cadbury would go on to dominate the British confectionery market and be responsible for some of the most famous brands - and advertising - in its market to the present day, notably Cadbury's Milk Tray (1915) and the 'All because the lady loves ...' line introduced in the early 1960s, followed by the man in black from 1968.
Cadbury's Flake emerged in 1920, advertised even then as the 'Crumbliest, flakiest chocolate in the world'. Then came Cadbury's Creme Eggs in 1971 and the 'How do you eat yours?' campaign to go with them in 1985.
Cadbury long ago recognised the value of its parent brand in selling its products. Since 1952 all Cadbury brands have carried its name on their wrappers - and advertising. When Cadbury took Crunchie into its family in 1981 it was remained Cadbury's Crunchie. Cadbury went on adding to its chocolate lines with Wispa (1983), Twirl (1985), Spira (1990) and Strollers (1991).
In 1969, the Cadbury brand became more than confectionery when it merged with Schweppes to create Cadbury Schweppes. The merged company became acquisitive in its bid to build a confectionery and soft drink giant, gobbling up Canada Dry (1986), Trebor (1989), Bassett's (1989), Dr Pepper and Seven Up (1995) and Snapple (2000). But in 1999 the company began to look for more focus in its operations. It sold its beverage businesses in more than 160 countries to Coca-Cola, keeping the drinks only in Australia, continental Europe and the US.
Cadbury also believes that it can effectively harness the enormous power of the company name and association with chocolate.
That association was reinforced when Cadbury became the first sponsor of the country's most popular soap, ITV's Coronation Street, in 1996.
At a cost of £10m for four years, the deal was the most expensive TV sponsorship ever signed. At first Cadbury could not promote particular chocolate bars - just the company name. But a change in Independent Television Commission regulations shortly afterward means the company is now able to create different sponsorship idents for different brands.
Cadbury is now firmly interwoven with British life. The Cadbury factory in Birmingham is now the theme park Cadbury World, which attracts half a million visitors a year.
Cadbury is also developing cafes for key locations around the country, with the first to open in Bath.
Its new product development has become more aggressive after a number of false starts in recent years. Cadbury's Heroes, the Dove Bar, ice cream brand extensions and Cadbury's cakes have all proved how strong the brand remains.
Managing for Value, the new-business model introduced by chief executive John Sunderland in 1997, has brought greater focus to the brands - and advertising campaigns - that are really working. But there is no greater compliment you can pay the brand than the fact that if you say 'chocolate' to millions of Britons they automatically think Cadbury's.
FACT FILE
1824
John Cadbury opens his grocer's shop, selling cocoa as a sideline, and
business starts to grow.
1899
Cadbury becomes a private company employing more than 2500 people at its
Birmingham factory.
1905
Launch of Cadbury's Dairy Milk, the flagship brand for years to come.
1969
Cadbury merges with Schweppes to become Cadbury Schweppes plc.
1988
Enters licensing agreement with Hershey Foods to manufacture and
distribute Cadbury products in the US.
1990
Opens Cadbury World theme park in Birmingham.
1996
Signs £10m deal to sponsor Coronation Street, ITV's long-running,
ratings-topping soap opera.