Britain's King Charles III and his wife Queen Camilla were crowned on Saturday during a religious ceremony stretching back more than one thousand years and steeped in ritual.

Around 2,200 guests, including 100 heads of state and members of the Japanese imperial family, crammed into London's Westminster Abbey to witness Britain's first coronation since 1953, when Queen Elizabeth II, who died in September, was crowned.

The Archbishop of Canterbury Justin Welby placed the magnificent solid gold St. Edward's crown, weighing 2.23 kilograms, upon the head of King Charles at noon with the congregation proclaiming, "God Save the King," as trumpets played and guns fired.

King Charles III stands after being crowned during his coronation ceremony in Westminster Abbey, on May 6, 2023 in London, England. (WPA Pool/Getty/Kyodo) 

Minutes earlier, the king was anointed with holy oil in the Christian ceremony, representing God's blessing on the king and queen and stretching back more than a thousand years.

The ceremony, full of pomp and pageantry, saw one of the biggest security operations in Britain's capital as police officers were on alert for terrorists and activists.

Tens of thousands of people braved the rain to line the procession route to the abbey as the royal couple was transported in a golden horse-drawn carriage.

The abbey has played host to coronations since 1066. King Charles was the 40th reigning monarch to be crowned there.

The Diamond Jubilee State Coach carrying Britain's King Charles III and Queen Consort Camilla travels from Buckingham Palace to Westminster Abbey for their coronation ceremony in London on May 6, 2023. (Kyodo) ==Kyodo

Among the chief overseas guests were U.S. first lady Jill Biden, French President Emmanuel Macron and, controversially, Chinese Vice President Han Zheng, who oversaw a civil liberties crackdown in Hong Kong. Crown Prince Fumihito and Crown Princess Kiko represented Japan.

Also present was the king's son, Prince Harry, who recently made several damaging claims about the royal family in a book.

During the ceremony, the king made a series of oaths, including a pledge to rule according to law in all realms and territories where he is head of state.

He also solemnly declared to maintain the Protestant reformed religion, honor the Church of England's legal settlement and exercise justice with mercy.

The ceremony, overseen by the Church of England's chief priest Welby, had the theme of "service" at its core, as the king pledged to serve the nation.

People watch the Diamond Jubilee State Coach carrying Britain's King Charles III and Queen Consort Camilla traveling from Buckingham Palace to Westminster Abbey for their coronation ceremony in London on May 6, 2023. (Kyodo) ==Kyodo

The king sat upon an ancient coronation chair used for more than 700 years for the anointing and crowning part of the ritual. During the anointing, which took place privately behind a screen, he was divested of his robes and wore a simple white shirt.

Following this, the 74-year-old, wearing a gold coat, was presented with several items of regalia, including a sword, bracelets, a ring and an orb, representing his authority and powers.

He was then handed two ceremonial staffs, holding one in each hand, before the special St. Edward's crown, dating from 1661 and only used for coronations, was placed on his head by the archbishop.

He was led to a ceremonial throne, where his son and heir, Prince William, paid homage to him.

Japanese Crown Prince Fumihito and Crown Princess Kiko leave a hotel in London on May 6, 2023, to attend King Charles III's coronation ceremony at Westminster Abbey. (Kyodo) ==Kyodo

This was followed by an invitation to the entire congregation, including those watching at home, to swear allegiance to the king, his heirs and successors.

Queen Camilla, 75, was crowned before being enthroned next to the king.

Organizers tried to make the Church of England ceremony more accessible to the wider public amid fears that the 1953 coronation format would appear outdated in a more diverse and multifaith nation.

The guests included more ordinary members of the public, including those who have served their local communities in various capacities. There were also fewer members of the aristocracy.

Another innovation included the presence of leaders from other faiths who took part in the procession.