France's President Francois Hollande (R) and Britain's Prince William (2R) unveil a commemorative plaque inside the World War I Thiepval monument northern France, on July 1, 2016 as Britain's Catherine, Duchess of Cambridge (2R) and Prince Harry (2) look, during the Somme battle's centenary commemorations. One week after Britain's vote to leave the European Union, Prime Minister David Cameron and royal family members will stand side-by-side with France's President to celebrate their historic alliance at the centenary of the deadliest battle of World War I. / AFP / POOL / Francois Mori (Photo credit should read FRANCOIS MORI/AFP/Getty Images)
