The Duchess of Cambridge "hasn't put a foot wrong" since she became a royal.
The 35-year-old Duchess married Prince William in 2011 and has been hailed by Hugo Vickers, author of biographies of the Queen Mother and the Duchess of Windsor, as having played her role perfectly until now.
He explained: "It's only natural that if you're in the third generation, you're going to play a supportive role. She's obviously a very important person, but you don't want to compete.
"The Queen Mother was the same when she was Duchess of York. There was Queen Mary and Queen Alexandra as well for a time, so she was rather a mousy figure for the first 13 years after she married Prince Bertie. Catherine hasn't put a foot wrong. She does her duties well, such as her involvement with the National Portrait Gallery and new role at Wimbledon."
The Duchess - who shares three-year-old Prince George and 20-month-old Princess Charlotte with her husband - has also been hailed as a devoted mother to her children.
Hugo told the National Post: "One thing I've been told about both Middleton sisters at Marlborough is that when they took anything on, they put their hearts and souls into it. Catherine's a supportive wife, a good daughter-in-law and a devoted mother."
The Duchess celebrated her 35th birthday on Monday (09.01.17) with her family at Anmer Hall in Norfolk, East Anglia.
The royal was joined by her husband Prince William, 34, and their two children at their country mansion for some low-key birthday celebrations.
The Duchess' parents and Charlotte's godmother, Sophie Carter, were also reported to have attended the bash.
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