LUXEMBOURG - MAY 11:  Catherine, Duchess of Cambridge (C) poses with Henri, Grand Duke of Luxembourg and Maria Teresa, Grand Duchess of Luxembourg during a visit to the Grand Ducal Palace on May 11, 2017 in Luxembourg. The Duchess is participating in the official commemoration of the 1867 Treaty of London and will attend a series of engagements to celebrate the cultural and historic ties between the UK and Luxembourg.  (Photo by Samir Hussein/WireImage)