Lionel Barber, the former editor of the Financial Times, discusses his fascinating biography of Masayoshi Son, one of the world's least-known but most consequential investors. Regarding himself as an 'empire builder' rather than a CEO, Son was briefly the world's richest man and has ruffled many feathers on his rise from a Korean slum in Japan to the modern-day temples of power. Russell Napier asks the questions.

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