LONDON — The French Tricolor and Britain’s Union flag hang from the standards near Windsor Castle. The carriages are primed, the tiaras polished.

French President Emmanuel Macron and his wife, Brigitte, arrived in Britain on Tuesday at the start of a state visit as the two countries highlight their long friendship with conspicuous displays of military pomp, golden carriages and royal toasts.

The backdrop for day one is Windsor Castle, a royal fortress for over 900 years that remains a working palace today.

Prince William and the Princess of Wales greeted the Macron’s at RAF Northolt outside London. King Charles III later formally welcomed the couple later at Windsor Castle, where they rode in a horse-drawn carriage and reviewed a military guard of honor. The first day will end with a state banquet at the castle.

Charles and Queen Camilla traveled to France in September 2023 in a visit that highlighted the historic ties between Britain and its closest European neighbor.

That royal trip came after years of sometimes prickly relations strained by Britain’s exit from the European Union and disagreements over the growing number of migrants crossing the English Channel on small boats.

President Macron’s arrival in Britain marks the first state visit by a French head of state since President Nicolas Sarkozy traveled to London in 2008.

State visits are ceremonial meetings between heads of state that are used to honor friendly nations and sometimes smooth relations between rivals. While the king formally issues the invitation for a state visit, he does so on the advice of the elected government.

State visits to Britain are particularly prized by heads of state because they come with a full complement of royal pomp and circumstance, including military reviews, carriage rides and a glittering state banquet hosted by the monarch.

The events normally take place in and around Buckingham Palace in central London. But the Macrons will stay at Windsor Castle, to the west of the capital. Buckingham Palace is undergoing extensive remodeling.

This is just the fifth state visit since King Charles ascended the throne in September 2022.

South African President Cyril Ramaphosa had the honor of receiving the first invitation for a state visit during the new king’s reign and spent three days in Britain in November 2022. The leaders of Qatar, Japan and South Korea have also received the full royal treatment.

More controversially, Charles has invited U.S. President Donald Trump to make an unprecedented second state visit to Britain, which is expected to take place in the autumn.

While Prime Minister Keir Starmer is trying to bolster relations with the U.S., some U.K. lawmakers have questioned whether Trump should be awarded such an honor after he torpedoed long-standing norms for global trade, refused to condemn Russian aggression in Ukraine and proposed moving Palestinians out of the Gaza Strip.

“An invitation for a state visit is highly prized amongst world leaders,’’ said Craig Prescott, a constitutional law expert at Royal Holloway, University of London, who focuses on the political role of the monarchy. “Now, it won’t necessarily turn an enemy into an ally, but it can be part of that broader diplomatic move to maybe get the best out of someone.

“It’s that cherry on the top, but at times it could be a very valuable cherry.”

Queen Elizabeth II, Charles’ mother, hosted 112 state visits during her seven decades on the throne.

State visits are nothing if not a showcase for the British military, which has a global reputation for putting on displays of spit-and-polish precision by soldiers wearing their iconic scarlet tunics and bearskin hats.

Active duty troops who rotate from operational assignments to ceremonial duties put in thousands of hours of training to ensure everything goes off without a hitch.

Some 950 service members from all branches of the U.K. military will take part in the ceremonies, including 380 on street-lining duties and 180 in the Guard of Honor at Windsor Castle. Six military bands will perform a selection of both British and French music.

The display is seen by the British government as a nod to close defense and diplomatic ties but also hints at the ambition for the visit, which may see new defense and security commitments.

But one horse will get special attention. The Macrons will visit Fabuleu de Maucour, a horse given by the French leader to the late Queen Elizabeth II in 2022, when the nation celebrated the Platinum Jubilee marking her 70 years on the throne.

Count on the French language to be used both in private and in public.

King Charles made a point of speaking French when he addressed lawmakers in the Senate chamber in Paris on the second day of his visit to France in 2023. During that speech, the king said the alliance between Britain and France was more important than ever as he recalled how the two nations had worked together to defeat the Nazi regime.

Charles was a frequent visitor to France before becoming king, making 35 official visits to the country as heir to the throne.