HAMBURG, GERMANY - JULY 21: Prince William, Duke of Cambridge, Catherine, Duchess of Cambridge, Prince George of Cambridge and Princess Charlotte of Cambridge visit two airbus helicopters during an official visit to Poland and Germany on July 21, 2017 in Hamburg, Germany. (Photo by Franziska Krug/Getty Images)
HAMBURG, GERMANY - JULY 21:  Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge visit to the Maritime Museum to celebrate the joint UK-German year of science, which for 2017 is focused on oceans, during an official visit to Poland and Germany on July 21, 2017 in Hamburg, Germany.  (Photo by Samir Hussein/WireImage)
HAMBURG, GERMANY - JULY 21:  Catherine, Duchess of Cambridge receives lessons to conduct an orchestra at Elbphilharmonie during day three of their official visit to Germany after two days in Poland on July 21, 2017 in Hamburg, Germany.  (Photo by Jane Barlow - Pool/Getty Images)
HAMBURG, GERMANY - JULY 21:  Prince George of Cambridge views helicopter models H145 and H135 before departing from Hamburg airport on the last day of their official visit to Poland and Germany on July 21, 2017 in Hamburg, Germany.  (Photo by Samir Hussein/WireImage)
HAMBURG, GERMANY - JULY 21: General view during the visit of the duke and duchess of Cambridge at the Hamburg Elbphilharmonie during an official visit to Poland and Germany on July 21, 2017 in Hamburg, Germany. (Photo by Franziska Krug/Getty Images)