Sir Victor Sassoon, the 3rd baronet and Shanghai real-estate magnate, was a man of wide interests. He was one of racing’s most successful owners, with four Derbies to his name, and famous for his magnificent collection of Chinese ivories and for his film-star friends. He also enjoyed photographing beautiful women, often with their clothes off. Every New Year’s Day, he wrote a recipe for the “cocktail of the year”. A Green Hat, for instance, consisted of 2/9 gin, 2/9 Cointreau, 2/9 French vermouth, 2/9 crème de menthe and 1/9 lemon juice.

We know much of this because the highly anglicised Sir Victor kept a diary – in English. His Sassoon ancestors, however, preferred the secrecy of an obscure Judeo-­Arabic script, indecipherable to previous historians until it was finally decoded by Professor Joseph Sassoon, descendant of another branch, and author of this book.

What Sassoon’s assiduous mining of the archives has produced is a family history writ large. And what that family was focused on was the rise and maintenance of its global trading empire. Thus, much of the book is a discussion of business practices, the twists and turns of negotiations, battles with rival firms, the establishment of new offices, the dealings with subordinates and so forth, which for some might be a bit of a trudge. That said, the story of the Sassoons’ rise from Ottoman Baghdadis to incalculably wealthy figures of the British Establishment is fascinating.

Baghdad, founded in the eighth century, soon became the commercial centre of the Islamic world. From early on, its Jews had handled money, one of the two heads of their community always being ­chosen by the ruling Ottoman pasha for the hereditary post of chief treasurer. In 1781, this was held by Sheikh Sassoon ben Saleh Sassoon. When he learnt of danger from a jealous rival, Sheikh Sassoon sent his son and heir, David, born in 1791, to the great trading centre of Basra, 500 miles south on the coast, soon following him as the province erupted into violence.

Much trade from India passed through Basra, and the Sassoons, learning of the comparative stability of large parts of India under the aegis of the East India Company, moved to Bombay in the mid-1820s. From the start, they aligned themselves with the British, building up a business empire, much of which was focused on the opium trade with China. “Whatever you touch turns to gold,” wrote the captain of a Sassoon steamship, thanking them for their philanthropy – another part of their business ethos.