LONDON, ENGLAND - MARCH 14:  Prince William, Duke of Cambridge, Catherine, Duchess of Cambridge and Prince Harry attend the Commonwealth Observance Day Service on March 14, 2016 in London, United Kingdom. The service is the largest annual inter-faith gathering in the United Kingdom and will celebrate the Queen's 90th birthday. Kofi Annan and Ellie Goulding will take part in the service.  (Photo by Samir Hussein/WireImage)