King Charles III's coronation: The biggest moments of the historic event

While not present for their coronation, U.S. President Joe Biden offered his congratulations to Charles and Camilla via Twitter.

"Congratulations to King Charles III and Queen Camilla on their Coronation," the president tweeted Saturday. "The enduring friendship between the U.S. and the U.K. is a source of strength for both our peoples. I am proud the First Lady is representing the United States for this historic occasion."

U.S. first lady Jill Biden, who attended the coronation in London, added her own message, tweeting: "The United States and the United Kingdom have a special relationship. It's an honor to represent the United States on this historic day at Westminster Abbey."

Charles selected his only sister, Princess Anne, to lead the procession from Westminster Abbey to Buckingham Palace.

Anne is following right behind Charles and Camilla on horseback as she leads a procession featuring 4,000 personnel, the largest military ceremonial operation of its kind since the queen’s coronation in 1953.

The newly-crowned king and queen departed in style from Westminster Abbey to travel back to Buckingham Palace in the Coronation Procession.

Their Majesties rode in the Gold State Coach, which has been used at every coronation since 1831.

The public last saw the Gold State Coach at the queen’s Platinum Jubilee celebration last year.

The congregation and choir join in singing the National Anthem as Charles and Camilla process out of Westminster Abbey.

The Robe of Estate worn by Charles was also worn by his grandfather King George VI in 1937. It is made of purple silk velvet and is embroidered in gold.

Camilla’s purple velvet Robe of Estate was designed and created for her by the Royal School of Needlework, of which she is patron. The design features hand-embroidered plants and insects, which were included to reflect her and Charles’ love of nature.