 At that time (around the 1920s), Cadbury and Rowntree's were England's two largest chocolate makers and they each often tried to steal trade secrets by sending spies, posing as employees, into the other's factory.Because of this, both companies became highly protective of their chocolate-making processes.It was a combination of this secrecy and the elaborate, often gigantic, machines in the factory that inspired Dahl to write the story.