King Charles III today became the 40th reigning monarch to be crowned at Westminster Abbey in a service interspersed with hymns, Bible readings and a liturgy underpinned by Christ's call to serve.

At his historic coronation, watched by millions around the world and over 2,000 guests inside the abbey, the St Edward's Crown was placed on his head by the Archbishop of Canterbury, the Most Rev Justin Welby.

He was crowned alongside Queen Camilla, with the pair being anointed by oil that was consecrated at the Church of the Holy Sepulchre in Jerusalem.

Thousands braved wet and grey conditions in London to catch a glimpse of the King and Queen as they made their way to the abbey in the horse-drawn Diamond Jubilee State Coach.

During the service, King Charles swore to do everything in his power to "maintain the Laws of God and the true profession of the Gospel" in his governance of the United Kingdom and Northern Ireland, and his realms and territories.

The theme of the coronation, 'Called to Serve', was reflected in the sermon of the Archbishop of Canterbury, who preached from Colossians 1:9-17 and Luke 4:16-21.

In his sermon, the Archbishop called service "love in action" and spoke about the humility of Christ, who although being the King of Kings, "put aside all privilege" for the cross and a crown of thorns.

"We are here to crown a King, and we crown a King to serve," he said.

"What is given today is for the gain of all. For Jesus Christ announced a Kingdom in which the poor and oppressed are freed from the chains of injustice. The blind see. The bruised and broken-hearted are healed.

"That Kingdom sets the aims of all righteous government, all authority. And the Kingdom also sets the means of all government and authority. For Jesus doesn't grasp power or hold onto status.

"The King of Kings, Jesus Christ, was anointed not to be served, but to serve. He creates the unchangeable law of good authority that with the privilege of power comes the duty to serve.

"Service is love in action. We see active love in our care for the most vulnerable, the way we nurture and encourage the young, in the conservation of the natural world. We have seen those priorities in the life of duty lived by our King."

The service continued ancient traditions handed down over successive coronations at Westminster Abbey over the last 1,000 years, but with some important changes, including for the first time ever an active role by female clergy and multi-faith leaders.

In an unprecedented addition to the coronation service, leaders and representatives of the Jewish, Buddhist, Sikh, Muslim and Hindu faiths delivered a greeting in unison to the King at the end of the service.

Another new element to the coronation was a brief exchange between the King and the Child of His Majesty's Chapel Royal, 14-year-old Samuel Strachan, upon entering the abbey, to whom he said, "In his name and after his example I come not to be served but to serve."

The coronation was attended by senior members of the Royal Family, including the Prince and Princess of Wales, and their three children, Prince George, 9, Princess Charlotte, 8, and Prince Louis, 5. Prince George served as one of King Charles' Pages of Honor. The Duke of Sussex was also in attendance.

After the service, the King and Queen departed the abbey and travelled through the streets of London in the Gold State Coach past cheering crowds.

Thousands of churches across the UK have been joining in the celebrations by holding coronation-themed events and livestreaming the service.

Speaking ahead of the coronation, Archbishop Welby said he had been praying that all people irrespective of faith or nationality would "find ancient wisdom and new hope", and be inspired to live lives " in service to others".

"This service reaches deep into our nation's Christian history," he said.

"From the ancient and sacred act of anointing monarchs, to the use of the sixth-century St Augustine Gospels, the service will link us in a profound way with our national story.

"But this is not simply history: I hope the service offers people an opportunity to hear the living words of God, which bring good news to every person in every generation.

"I also hope and pray that the Coronation will serve as a powerful reflection and celebration of who we are today, in all our wonderful diversity."