The title “King of Diamonds” does not refer to a single individual but is often used figuratively to describe several notable figures in the diamond industry or individuals known for their significant involvement in the diamond trade. The title may be attributed to various people at different times based on their achievements or contributions to the diamond business. Some of the people who have been referred to as the “King of Diamonds” in the world of diamonds and jewelry include:

1. Cecil Rhodes: Cecil Rhodes was a British businessman, mining magnate, and politician who played a pivotal role in the diamond industry. He founded the De Beers Mining Company, which went on to dominate the global diamond market. His influence in the diamond trade earned him the nickname “Colossus of Rhodes.”
2. Sir Ernest Oppenheimer: Sir Ernest Oppenheimer was a key figure in the diamond industry in the early 20th century. He became the chairman of De Beers Consolidated Mines Ltd. and played a significant role in shaping the modern diamond market.
3. Barney Barnato: Barney Barnato was a prominent figure in the diamond and gold mining industry in South Africa during the late 19th century. He was a key player in the amalgamation of diamond mines that eventually led to the formation of De Beers.
4. Harry Winston: Harry Winston was a renowned American jeweler and gem dealer known for acquiring some of the world’s most famous diamonds, including the Hope Diamond. His name is associated with high-end diamond jewelry and rare gemstones.
5. Laurence Graff: Laurence Graff is a British jeweler and founder of Graff Diamonds, a luxury jewelry brand known for dealing in some of the world’s most exceptional diamonds. Graff is often referred to as the “King of Diamonds” due to his involvement in acquiring and cutting some of the largest and most famous diamonds in history.

The title “King of Diamonds” is not an official or formal designation but rather a colloquial term used in the context of the diamond industry to recognize influential figures and companies. Different people or companies may be associated with this title at different times in history, depending on their impact on the diamond trade.