Prince William, Duke of Cambridge And Catherine, Duchess Of Cambridge At America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge visits the Land Rover BAR at the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge visits the Land Rover BAR at the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge visit the Land Rover BAR at the America's Cup World Series on July 24, 2016 in Portsmouth, England.

The Duke and Duchess of Cambridge pose with members of the 1851 Trust charity as they visit the Land Rover BAR at the America's Cup World Series on July 24, 2016 in Portsmouth, England. 

(R) Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge visit the Land Rover BAR at the America's Cup World Series on July 24, 2016 in Portsmouth, England.

 Prince William, Duke of Cambridge meets a young member of the 1851 Trust charity and CEO Jo Stocks as he visits the Land Rover BAR at the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge visits the Ben Ainslie Racing team base on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge visits the Ben Ainslie Racing team base on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge visit the Ben Ainslie Racing team base on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge visits the Ben Ainslie Racing team base on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge visit the Ben Ainslie Racing team base on July 24, 2016 in Portsmouth, England. 

 Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge visit the Ben Ainslie Racing team base on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge visits the Ben Ainslie Racing team base on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge meets members of the 1851 Trust during a visit to Land Rover BAR at the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge visits Land Rover BAR boat shed at the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge meets members of the 1851 Trust during a visit to Land Rover BAR at the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge leave the Ben Ainslie Racing team base to go and watch the racing on The Solent on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge leave the Ben Ainslie Racing team base to go and watch the racing on The Solent on July 24, 2016 in Portsmouth, England. 

Catherine, Duchess of Cambridge is seen on stage at the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge are seen on stage at the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge ride in the front of a boat as they watch the America's Cup World Series Race on the Solent on July 24, 2016 in Portsmouth, United Kingdom. The royal couple visited the home of the British competitors for the America's Cup before observing the ongoing competition.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge attend the America's Cup World Series on July 24, 2016 in Portsmouth, England. 

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge attend the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge attends the trophy presentation of the America's Cup World Series on July 24, 2016 in Portsmouth, England. 

Catherine, Duchess of Cambridge visits Land Rover BAR during the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge visit Land Rover BAR during the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge visit Land Rover BAR during the America's Cup World Series on July 24, 2016 in Portsmouth, England.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge visit Land Rover BAR during the America's Cup World Series on July 24, 2016 in Portsmouth, England.