President Donald Trump was welcomed with full royal pageantry, including military honor guards and mounted troops, as he joined King Charles III at Windsor Castle on Wednesday to begin a state visit marked by both spectacle and political risk for Britain.

Prince William and his wife, Catherine, met Trump's helicopter as it landed in the private Walled Garden on the vast estate, and they walked the American president and first lady Melania Trump over to be greeted by the king and Queen Camilla.

The guests traveled to the castle in a procession of horse-drawn carriages, past ranks of soldiers, sailors and aviators, as military bands played the U.S. and British national anthems.

The king and the Republican president chatted in the Irish State Coach during the short journey to the castle quadrangle, where Trump, accompanied by Charles, inspected an honor guard of soldiers in red tunics and bearskin hats.

The day of pageantry, the highlight of Trump's second state visit to Britain, was on a scale designed to impress the grandeur-loving president and involved some 120 horses and 1,300 troops, including the largest guard of honor in living memory.