The Cadbury's Dairy Milk recipe still continues to be a secret and is kept in a safe at the Bournville factory.

Cadbury's intention was to come up with a chocolate with higher milk content. After making big investments in the acquiring new machines and researching the development of the recipe, Cadbury was ready with a formula by June 1904.

February 26, 1932: Two women at the Cadbury's chocolate factory in Bournville, in the West Midlands join together chocolate Easter egg halves.

Photograph: Fox Photos/Getty Images

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