The Duke and Duchess of Sussex have begun repaying the cost of renovating their UK home

The couple are keeping the cottage as their English base and, according to the Mail on Sunday newspaper, it was "quietly arranged" last month for them to pay just under £18,000 a month to retain the abode.

The sum is more than the commercial rate but allows them to contribute towards the renovation bill - which was initially covered by the taxpayer-funded Sovereign Grant - with the excess.

It is estimated that it will take over 11 years of payments at the current level to cover the cost of the renovations, without taking into account interest or the running costs of the cottage.

The changes made to the property were detailed last summer.

The Sovereign Grant covered the cost of replacing heating, electric, gas and water main systems, as well as replacing ceiling beams and floor joists at the property, which has been remodelled from five separate living quarters into one residence.

Harry and Meghan were also permitted to use the grant to install a "certain standard" of kitchen, bathroom, flooring and fitted furniture from the grant, but anything considered a "higher spec" than that approved by the palace must be met by the couple themselves.

Sir Michael Stevens, Keeper of the Privy Purse, who is responsible for monarchy's accounts, said of Frogmore Cottage at the time: "The property had not been the subject of work for some years and had already been earmarked for renovation in line with our responsibility to maintain the condition of the occupied royal palaces estate.

"The Sovereign Grant covered the work undertaken to turn the building into the official residence and home of the Duke and Duchess of Sussex and their new family.

"The building was returned to a single residence and outdated infrastructure was replaced to guarantee the long-term future of the property.

"Substantially all fixtures and fittings were paid for by Their Royal Highnesses."