LUXEMBOURG - MAY 11:  Catherine, Duchess of Cambridge with Duchess Stephanie of Luxembourg and Hereditary Grand Duke Guillaume of Luxembourg visit the Drai Eechelen Museum during a one day visit on May 11, 2017 in Luxembourg. The Duchess will attend a series of engagements to celebrate the cultural and historic ties between the UK and Luxembourg and the official commemoration of the 1867 Treaty of London, which confirmed Luxembourg's independence and neutrality.  (Photo by Tim Rooke - Pool/Getty Images)