National Service Of Thanksgiving To Celebrate The Queen's 90th Birthday [Getty Images]

LONDON, ENGLAND - JUNE 10: Catherine, Duchess of Cambridge attends a National Service of Thanksgiving as part of the 90th birthday celebrations for The Queen at St Paul's Cathedral on June 10, 2016 in London, England. (Photo by Danny Martindale/WireImage) — see more

LONDON, ENGLAND - JUNE 10: Catherine, Duchess of Cambridge attends a National Service of Thanksgiving as part of the 90th birthday celebrations for The Queen at St Paul's Cathedral on June 10, 2016 in London, England. (Photo by Danny Martindale/WireImage)

WireImage Danny Martindale