The concept is hardly new; John Rockefeller set up his family office in 1882. But the number has exploded this century. Somewhere between 5,000 and 10,000 are based in America and Europe and in Asian hubs such as Singapore and Hong Kong. Though their main task is to manage financial assets, the biggest offices, some with hundreds of staff, undertake all sorts of other chores, from tax and legal work to acting as high-powered butlers who book jets and pamper pets.
