Prince Harry and Megan's Frogmore Cottage has been renovated with STG2.4 million ($A4.4 million) of British taxpayers' money, royal accounts have revealed.
The Duke and Duchess of Sussex's country residence, close to Windsor Castle, underwent major work to turn five properties back into a single home for the couple and their baby son Archie.
All fittings and fixtures were privately paid for by Harry and Meghan.
It is likely they installed a luxury kitchen and bathroom and the residence has reportedly been designed by the couple with entertaining in mind and with extra bedrooms to accommodate guests, such as Meghan's mother Doria Ragland.
Accounts for the Sovereign Grant, which funds the Queen and her household's official expenses, show the monarchy cost the British taxpayer STG67m ($A123m) during 2018-19 - an increase of almost STG20m ($A37m) on the previous financial year.
A large amount of the rise was due to work updating the decades-old services at Buckingham Palace and maintaining the occupied royal palaces.
Keeper of the Privy Purse Michael Stevens, who is responsible for the monarchy's accounts, said Frogmore Cottage "had not been the subject of work for some years" and had been earmarked for renovation.
"The building was returned to a single residence and outdated infrastructure was replaced to guarantee the long-term future of the property," he said.
"Substantially all fixtures and fittings were paid for by Their Royal Highnesses."
Harry and Meghan moved from their Nottingham Cottage home in the grounds of Kensington Palace to Frogmore Cottage, a Grade II listed mid-Victorian building in Home Park near Windsor Castle, ahead of the birth of Archie.
A royal source said the major work on the couple's cottage included replacing defective wooden ceiling beams and floor joists, and outdated and inefficient heating systems were updated.
The home also needed substantial new electrical rewiring, including its own electrical sub-station, and new gas and water mains were installed.
The renovation took around six months and was completed a few months before Archie was born on May 6.
Some works remain to be completed, such as repainting the exterior.
Frogmore Cottage was a gift from Harry's grandmother the Queen, who was kept updated on the work.
Australian Associated Press
