American actress Grace Kelly, Princess of Monaco (1929 – 1982) as she attends an unspecified event, Philadelphia, 1959. Kelly’s Cartier diamond necklace nearly outshined her engagement ring.

The most expensive royal engagement ring belongs to Grace Kelly, the Hollywood actress who became Princess of Monaco. Kelly’s Cartier ring was given to her by Prince Rainier III in 1956.

Either way, this eternity ring appears to be a temporary replacement for Kate’s most iconic piece of jewelry, her sapphire and diamond engagement ring that once belonged to Princess Diana.A ...