Britain's Catherine, Duchess of Cambridge (L), Britain's Prince William, Duke of Cambridge (2nd L), former athletes Iwan Thomas, and Paula Radcliffe and Britain's Prince Harry (R), pose for a photograph at a training event to promote the charity Heads Together, at the Queen Elizabeth Olympic Park in London, on February 5, 2017.

The Duke and Duchess of Cambridge and Prince Harry join a training day with the runners taking part in the 2017 Virgin Money London Marathon for Heads Together, the official Charity of the Year. / AFP PHOTO / POOL / Alastair Grant        (Photo credit should read ALASTAIR GRANT/AFP/Getty Images)