Duchess Catherine and her sister Pippa Middleton have been praised as "tough" women.
The royal and her sibling have found themselves in the public eye ever since Catherine - previously Kate Middleton - married Prince William in April 2011 but their former teacher at Berkshire prep school St Andrew's Kevin Allford, says the sisters can handle their fame.
He told the Daily Mail newspaper: "They were both tough.
"Though Pippa was tougher than her sister, better at taking knocks than Catherine."
Allford also spoke of the sisters' close relationship, and said there was never a rivalry between the pair.
He added: "There was never fierce competition between the girls.
"One never said to the other: 'I can beat you.'"
Catherine and Pippa are so close that Pippa often keeps her company while William is busy with his career as a search and rescue pilot.
A source previously said: "Pippa recently spent time with Catherine in Wales, which Catherine loved, and William is relieved because Pippa will be able to keep an eye on her sister and make sure takes care of herself!"