But as workmen put the finishing touches to the renovations that lasted for two years, the couple are returning to London to start family life in their first "proper" home.
"They can't wait. They are so looking forward to getting the place how they want it and being settled," a friend was quoted as saying by the Daily Express.
The Duke and Duchess of Cambridge are to move into the four-storey 20-room apartment 1A, which once belonged to Princess Margaret, Queen Elizabeth II's sister who died in 2002.
Unlike the neighbouring apartment where William and his brother Harry grew up, 1A has a large secluded garden.
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And the move comes just in time for the new-born prince's christening ceremony on October 23 in the Chapel Royal at St James' Palace.
It is believed that the Queen gave Kate permission to choose priceless antiques from the Royal Collection to furnish her new home.
Kate, who has a degree in art history, has overseen the decorations herself and has been spotted shopping for fabrics in the upmarket Chelsea Design Centre.
A modern kitchen has been installed, and an environmentally-friendly heating and hot water system.
Meanwhile, renovation work has begun on Anmer Hall, the Georgian mansion at Sandringham which will become William and Kate's country retreat.
Diggers are removing topsoil to create a new drive, which will afford the couple greater privacy.