Prince William and Princess Kate visit Poland

Britain's Kate, the Duchess of Cambridge holding Princess Charlotte, Prince William and Prince George walk past the honor guard, during the arrival ceremony, in Warsaw , Poland, Monday, July 17, 2017. The Duke and Duchess of Cambridge and their children have arrived in Poland, the first leg of a goodwill trip to two European Union nations that seeks to underscore Britain's friendly ties despite its negotiations to leave the bloc. [Photo: AP/Czarek Sokolowski]

Catherine, The Duchess of Cambridge and Prince William with President Andrzej Duda and his wife, Agata, at the Presidential Palace on day one of their visit to Poland. [Photo: Star Max 2 via AP]

Children welcome Britain's Kate, the Duchess of Cambridge, during her visit with Britain's Prince William, in front of the presidential palace, in Warsaw, Poland, Monday, July 17, 2017. The Duke and Duchess of Cambridge and their children arrived in Poland on Monday, on the first leg of a goodwill trip to two European Union nations that seeks to underscore Britain's friendly ties despite its negotiations to leave the bloc. [Photo: AP/Alik Keplicz]

Prince William and Catherine, Duchess of Cambridge attend a Garden reception at The Orangery, Lazienki Park, Warsaw, Poland, on the 17th July 2017. [Photo: Star Max 2 via AP]