Britain’s King Charles arrived at the White House on Tuesday for a meeting with US President Donald Trump, as part of a state visit intended to underscore unity between the two long-time allies, despite deep divisions over the Iran war.

Charles and Queen Camilla were greeted by the president and first lady Melania Trump for a morning visit to the presidential mansion while hundreds of guests stood on the South Lawn with the Washington Monument in the distance.

Cannons boomed, temporarily...