LONDON, ENGLAND - APRIL 23: Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge joke at the starting line as they cheer on runners as they signal the start of the 2017 Virgin Money London Marathon on April 23, 2017 in London, England. (Photo by Chris Jackson/Getty Images)
LONDON, ENGLAND - APRIL 23: Prince William, Duke of Cambridge, Catherine, Duchess of Cambridge and Prince Harry cheer on runners as they signal the start of the 2017 Virgin Money London Marathon on April 23, 2017 in London, England. (Photo by Chris Jackson/Getty Images)
LONDON, ENGLAND - APRIL 23: Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge helping at a water station during the 2017 Virgin Money London Marathon on April 23, 2017 in London, England. (Photo by Mark Cuthbert/UK Press via Getty Images)
LONDON, ENGLAND - APRIL 23: Catherine, Duchess of Cambridge helping at a water station during the 2017 Virgin Money London Marathon on April 23, 2017 in London, England. (Photo by Mark Cuthbert/UK Press via Getty Images)
LONDON, ENGLAND - APRIL 23: Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge with Prince Harry cheering on runners during the 2017 Virgin Money London Marathon on April 23, 2017 in London, England. (Photo by Mark Cuthbert/UK Press via Getty Images)
