Prince William and Kate Middleton's Kensington Palace home is undergoing extensive refurbishment costing £1million ahead of the arrival of the royal baby.
Apartment 1A of the central London residence is undergoing a complete overhaul which is due to be completed this autumn.
Interior renovations on the 21-room abode, the former home of Princess Margaret , have cost £600,000. A further £400,000 was spent on repairs to the roof.
The prospective family home has had its heating, water and electrical systems replaced. Essential works to clear asbestos contamination have also been carried out.
William and Kate, who are currently living in the modest two-bedroom Nottingham Cottage in the palace grounds, are expected to move into the 21-room property with their new baby in the autumn once the works are complete.
Their new home was last lived in by Princess Margaret and had not been refurbished since the early Sixties.
While the home is described as an apartment, the term is misleading.
Apartment 1A is in fact a four-storey house and comprises staff quarters, a nursery, extensive living quarters, entertaining space and a walled garden.
It forms half of the Clock Tower wing, designed by Sir Christopher Wren for King William and Queen Mary in the 17th century.
The renovations will allow William, Kate and Prince Harry to accommodate their private and press offices at Kensington Palace, or 'KP' as Princess Diana used to call it.
Overall, there was a £9.1million bill for maintaining the royal properties and palaces for 2012-2013.
Buckingham Palace accounts revealed that the public bill for running the monarchy over the past year has amounted to £33.3million, up £900,000 or 2.6 per cent from the previous year.
The Palace insisted that the net expenditure for 2012-2013 was a small reduction in real terms after inflation.
"The Royal Household has continued to reduce its expenditure funded by the taxpayer in successive years since 2008-9, achieving a real terms reduction of 24 per cent over the last five years," said Sir Alan Reid, Keeper of the Privy Purse.
The Palace said that the £33.3 million overall cost to the taxpayer is the equivalent of 53p a year to every person and represents an 80 per cent fall in real terms since 1994.