Monaco Royals Whose Deals Have Brought Peril to the Palace Doors

For the better part of two decades, the man Prince Albert II of Monaco trusted with his money and his secrets was an accountant who served at the monarch’s beck and call. About once a month they met alone in the Palais Princier to discuss the running of the country, 500 acres of rock between the Alps and the Mediterranean Sea that’s been ruled by the same dynasty for 700 years.

The adviser, Claude Palmero, prided himself on discretion. He kept part of the royal family’s fortune hidden in Panama. When the prince’s wife blew past her allowance, Palmero balanced ...