The coronation of King Charles III and Queen Camilla

In a slight deviation from tradition, the couple are processing to the ceremony in the Diamond Jubilee State Coach drawn by six Windsor Grey horses. They are being accompanied on the 1.3-mile route by four divisions of the sovereign’s most trusted bodyguards, the Household Cavalry.

Each division consists of 24 horses with two divisions of the Blues and Royals at the front, and two divisions of the Life Guards following.

The procession is being led by the Household Cavalry Mounted Band – that's 48 horses and musicians, who will play eight marches as they travel the route.

The coach’s interior is immaculately upholstered in primrose yellow silk and inlaid with materials tied to Britain and its history.

“It’s a real microcosm of British and world history. There’re woods from the royal residences, from explorations and from other countries and nations as well,” explained Sally Goodsir, the Royal Collection Trust’s curator of decorative arts ahead of today's celebrations.

Royal fans from all over the world have gathered on the streets of London, decked out in flags, crowns and homemade regalia.

But what about for those in the US who haven’t made the trip across the pond?

Here's what you need to know:

After the ceremony, the newly crowned King Charles and Queen Camilla will travel back to Buckingham Palace in the Gold State Coach, which has been used in every coronation since 1831, accompanied by a grand procession and display of British pageantry.

They will then make an appearance on the palace balcony alongside members of the royal family and watch a flypast of 60 aircraft, scheduled to last six minutes.

Haven't kept up with recent royal happenings? Here's a full breakdown of everything you need to know.

The Governors-General and Prime Ministers of the Commonwealth realms -- or the dignitaries sent in their place -- have entered the Abbey in a procession before the ceremony begins.

Some history: The British Empire was at its greatest height by the end of the 19th century. However, the 20th century saw the country’s supremacy crumble as its colonies struggled and gained independence. Today, King Charles III is the head of a significantly shrunken empire, which over time transitioned into the “British Commonwealth.”

However, the hold of the sovereign over the British Commonwealth also loosened over time.

Earlier, the Commonwealth required allegiance to the Crown. But in 1949, “British” was dropped from the name.

And today, the Commonwealth of Nations is an association of sovereign states that focus efforts on trade, international cooperation, social issues and environmental concerns.

The position of its head is not hereditary. King Charles III was selected to be the head by the member nations in 2018.

Most of the member nations in this association don’t recognize the British monarch as their head of state — Barbados was the most recent country that removed the Queen as its head of state, 55 years after it declared independence from Britain.

Other Caribbean countries, such as Jamaica, have indicated they intend to do the same.

Additionally, while the group largely has erstwhile British colonies, some members of the Commonwealth today were never part of the Empire. For example, Rwanda and Mozambique became members in 2009 and 1995 respectively. Gabon and Togo joined most recently in June 2022.

In addition to the UK, King Charles is the head of state in 14 Commonwealth countries — or realms — including Australia, Canada and New Zealand.

With the British Empire virtually gone and the Commonwealth of Nations in its new era, some are asking how relevant the body still is, given its roots in Empire.

Ultimately, King Charles III ascends the throne in an era where the role of the British monarch looks dramatically different from the time when his mother Queen Elizabeth II was crowned.

King Charles and Queen Camilla have left Buckingham Palace, traveling in the Diamond Jubilee State Coach on the short journey to Westminster Abbey. They are both dressed in their respective Robes of State.

Here's the route they'll be taking shortly:

Britain's Prime Minister Rishi Sunak has entered Westminster Abbey, moments after all of the UK's living former premiers arrived.

Tony Blair, Gordon Brown, John Major and David Cameron all entered the Abbey first. They were quickly joined by Theresa May, Boris Johnson and Liz Truss -- who led the country for a few, chaotic weeks last year.

Earlier, French President Emmanuel Macron entered the venue. European Commission President Ursula Von der Leyen and European Council President Charles Michel have also arrived, as has Bahrain’s King Hamad bin Isa Al Khalifa.

Arson. Bumbling bishops. A jilted spouse banging on the abbey door.

Compared to these moments that have punctuated British coronations throughout history, the British weather potentially raining on King Charles III’s parade is nothing at all.

Coronations at Westminster Abbey go back almost a thousand years. They have become a well-rehearsed, finely tuned machine. Yet, despite all the pomp and ceremony, there have been times when they have gone disastrously wrong.

When William the Conqueror was crowned on Christmas Day 1066, the atmosphere both inside and outside the abbey was tense, coming just months after William had earned his conqueror moniker by vanquishing Harold Godwinson at the Battle of Hastings.

When those inside the abbey enthusiastically proclaimed “God save the King,” the noise reached such a level that William’s guards outside believed an assassination attempt must be underway. They then proceeded to take the only rational course of action - promptly burning down a number of buildings in the local area.

George IV’s coronation in 1821 featured drama that would make the writers of most soap operas blush. The King had decided to exclude his wife, Queen Caroline, from the service and ordered those guarding the entrances to Westminster Abbey to refuse her entry.

Despite trying every entrance to the Abbey, she was not able to make it inside and had to leave.

During Queen Victoria’s 1837 coronation, the young monarch was left in agony when the Archbishop of Canterbury forced the coronation ring onto the wrong finger. She also had to be rushed back into the abbey because the Bishop of Bath and Wells had accidentally omitted the section of the service in which she officially became Queen.

Remarkably, there are even more coronation blunders and you can read the full story here.

Processions into the abbey have started with faith leaders walking in first. They will be followed by representatives from each of the realms where the King is head of state. The flagbearers of each nation will be accompanied by the governors general and prime ministers. 

This is the first time non-Protestant faith leaders have been given a role in a coronation. One of many firsts we'll see during the Anglican service, the theme of which is “called to serve.”

Others include the King praying aloud, the involvement of female clergy and the incorporation of other languages spoken in the British Isles.

Buckingham Palace has revealed some of the historical items King Charles III will don for his coronation ceremony on Saturday, including items previously worn by his mother and grandfather for their own crowning moments. 

The British monarch will be draped in a sleeved coat of gold cloth, known as the "Supertunica," and the "Imperial Mantle" — a gold priestly-style robe, woven with colored threads — both worn by his mother, Queen Elizabeth II, for her own coronation in 1953. 

These "vestment" pieces are just some of the intricate items that will make up the coronation robes worn during the ceremony at Westminster Abbey in London. 

Both items are normally on display in the Tower of London and were last worn by Charles' mother at her coronation.

The whole look: The Supertunica was made in 1911 for the coronation of King George V and was later worn by King George VI for his 1937 coronation.

The full-length embroidered coat will be fastened at the waist with a "Coronation Sword Belt." This belt is made of gold cloth and embroidered in gold thread. Lined in dark red silk, it has a gold buckle and clip used for attaching the jeweled "Sword of Offering" presented to the monarch during the ceremony.

Worn over the Supertunica is the large gold cloak called the Imperial Mantle, which was made for the 1821 coronation of King George IV and has been reused by British monarchs since. It is draped over the sovereign’s shoulders and trails on the ground at the side and back. Its intricate details include emblems of crowns and fleur-de-lis, plus colored roses, thistles and shamrock. 

When it comes to accessories, King Charles will also have a "Coronation Gauntlet" – effectively a fancy white leather glove, embroidered with national emblems including the Tudor rose, thistle, shamrock, oak leaves and acorns.

First lady Jill Biden has arrived at Westminster Abbey and taken a seat next to Ukraine's first lady, Olena Zelenska.

Biden wore blue while her granddaughter, who is joining the first lady, wore yellow - matching Ukraine's national colors.

WATCH HERE:

Dozens of leaders will be heading to the Abbey but US President Joe Biden, leader of one of the UK’s closest allies, is not present. 

Instead, the first lady is leading the US delegation. Jill Biden, who is traveling with her granddaughter Finnegan Biden, touched down in England late Thursday evening and takes on a packed schedule of events on the three-day trip. The first lady said it was an "honor to represent the United States for this historic moment and celebrate the special relationship between our countries."

Meanwhile, President Biden spoke on the phone with King Charles III on April 4 to underscore “the strength of relationship between our countries and the friendship between our peoples,” a White House readout of the call said.

That may, on the surface, seem odd given the US-UK special relationship. But actually, it's worth noting that no American president has ever attended a British monarch’s coronation, as US officials noted when reports first emerged of Biden’s absence.

Biden has already “conveyed his desire to meet with the King in the United Kingdom at a future date,” according to the White House readout of the call with King Charles.

Both the president and the first lady traveled to London in September to attend the funeral of Queen Elizabeth II, who reigned for 70 years.

Thirteen other presidents sat in the Oval Office during the late Queen’s reign, and she met all of them, except for Lyndon Johnson.

Barack Obama called her “truly one of my favorite people,” while Ronald Reagan bonded with her over country life and Bill Clinton was impressed by her political aptitude.