Cambridge's Duke and duchess Prince William and Kate Middleton are seen ahead of the Six Nations tournament Rugby Union match between France and Wales at the Stade de France in Saint-Denis, outside Paris, on March 18, 2017. (Photo by Geoffroy Van der Hasselt/NurPhoto via Getty Images)

Cambridge's Duke and duchess Prince William and Kate Middleton are seen ahead of the Six Nations tournament Rugby Union match between France and Wales at the Stade de France in Saint-Denis, outside Paris, on March 18, 2017. (Photo by Geoffroy Van der Hasselt/NurPhoto via Getty Images)

Cambridge's duchess Kate Middleton is seen ahead of the Six Nations tournament Rugby Union match between France and Wales at the Stade de France in Saint-Denis, outside Paris, on March 18, 2017. (Photo by Geoffroy Van der Hasselt/NurPhoto via Getty Images)

Cambridge's duchess Kate Middleton is seen ahead of the Six Nations tournament Rugby Union match between France and Wales at the Stade de France in Saint-Denis, outside Paris, on March 18, 2017. (Photo by Geoffroy Van der Hasselt/NurPhoto via Getty Images)

Cambridge's Duke and duchess Prince William and Kate Middleton are seen ahead of the Six Nations tournament Rugby Union match between France and Wales at the Stade de France in Saint-Denis, outside Paris, on March 18, 2017. (Photo by Geoffroy Van der Hasselt/NurPhoto via Getty Images)

Cambridge's Duke and duchess Prince William and Kate Middleton are seen ahead of the Six Nations tournament Rugby Union match between France and Wales at the Stade de France in Saint-Denis, outside Paris, on March 18, 2017. (Photo by Geoffroy Van der Hasselt/NurPhoto via Getty Images)

The Duke and Duchess of Cambridge during the RBS 6 Nations match at the Stade de France, Paris. (Photo by David Davies/PA Images via Getty Images)

The Duke and Duchess of Cambridge during the RBS 6 Nations match at the Stade de France, Paris. (Photo by David Davies/PA Images via Getty Images)

The Duchess of Cambridge during the RBS 6 Nations match at the Stade de France, Paris. (Photo by David Davies/PA Images via Getty Images)

The Duchess of Cambridge during the RBS 6 Nations match at the Stade de France, Paris. (Photo by David Davies/PA Images via Getty Images)