The ceremony was also attended by Prince Charles, his sons, and Diana's brother Earl Spencer.
The construction was designed by the American landscape architect and master of land art Catherine Gustafson and cost 3.6 million pounds.
The fountain is a ring of light granite slabs, along which two streams of water flow towards each other. The opposite diameters of the oval are 50 and 80 meters.
Water flowing in the east direction flows along the steps, and in the west it imitates a babbling stream. Both streams meet in a rounded pond, from where water again flows into the "source" of the fountain.
This project was selected from 10,000 entries submitted for the competition; in the final, the jury preferred it to a more radical version of the sculptor Anish Kapoor.