The nanny, in her late thirties, has worked in Britain for the past couple of decades for other wealthy families, The Daily Express reported.
The Duke and Duchess of Cambridge have taken her on to replace 71-year-old Jessie Webb, William's nanny when he was a little boy, who was brought out of retirement to help the couple temporarily after George was born in July last year.
Kate, 32, initially said she did not need a full-time nanny but the couple have bowed to the inevitable and taken on the new help ahead of what promises to be a gruelling three-week tour of New Zealand and Australia next month.
The nanny is, however, not in charge of the third in line to the throne this week.
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Kate's parents, Mike and Carole Middleton are looking after the infant while his parents enjoy a romantic, exotic week-long holiday, a second honeymoon, at a five star hotel resort in the Maldives.
Palace officials have declined to discuss the identity of the new nanny, who was spotted walking Prince George in his pram in Hyde Park last week alongside a police bodyguard but the name of the woman who will play a key role in the upbringing of the future King is expected to emerge soon.
"She is not married and does not have a boyfriend, as her life is totally dedicated to the family she is working with. She is known for being totally professional - married to the job," the friend was quoted as saying.