Undaunted by the erosion in the worth of the world’s wealthy during the credit crunch, several private banks are moving upmarket by developing services which target families with $30m (€21m) or more to invest.

They hope to take advantage of clients' dismay at the fallen value of their fortunes, and the defection of advisers from troubled banks, notably UBS. However, those developing new services may be overly optimistic about the fees they can earn from them.