Opinion: Trump strolling around Windsor Castle, as if he belongs, flies in the face of all the causes Charles has stood for throughout his life, writes .

The Royal Family has played a big role in President Trump's visit to the United Kingdom. Craig Prescott, author of "Modern Monarchy," explains how the U.K. government uses the Royals as leverage.

The start of the second official trip of the President of the United States was mainly ceremonial: walks around Windsor, a floral tribute to Queen Elizabeth II, and a lunch with the Kings and the heirs.

"This historic event will help renew the link between the monarchy and Catholicism which was broken at the Reformation," said Timothy Guile, chairman of the English Catholic History Association.

Thousands of demonstrators packed London streets Saturday for a march organized by far-right activist Tommy Robinson.

Trump has long expressed fascination with the royal family. The U.K. government will tap into that this week during a state visit that combines pageantry and politics.

Britain welcomed Trump “like the king he wants to be,” CNN observed. But London knew exactly what it was doing, the network added, noting that the British monarchy “has been in the business of dealmaking since long before Trump was born.

No one in London had been able to take Trump’s positive attitude as a given. The meeting between the two leaders had promised any number of traps and hazards, but the opening bid of a missive from the 76-year-old hereditary sovereign of the United Kingdom had been decisive. The state visit will take place in a few days, from Sept. 17 to 19.

On a rare trip back to the U.K., devoted mostly to charity events, Prince Harry may have begun the reconciliation with his family he's said he wants.

On this day in 2015, Queen Elizabeth made history by shattering a record once held by her great-great-grandmother, Queen Victoria. The achievement marked a defining moment in her service to the United Kingdom and added a remarkable chapter to her royal legacy.

Since January Trump has claimed the right to govern autocratically, relying on medieval Europe’s time-honored historical model.