All newlyweds know that moving house can be an expensive business, but when you are a royal couple the costs can go through the palace roof. The surprise takeaway from today’s Sovereign Grant Report for 2018-19 is that the refurbishment of Frogmore Cottage, Harry and Meghan’s new home on the Windsor estate, will set taxpayers back £2.4m.

We are told by palace aides that the 19th-century Grade II-listed property was already earmarked for renovation, and that “substantially all fixtures and fittings were paid for by their royal highnesses” – but now that the final bill has arrived, it looks like the division of costs has greatly favoured the royals.

But should we be surprised? Historically, when the Windsors move house the taxpayer gets landed with a kingsize bill. When the newly married Princess Elizabeth and Prince Philip took possession of Clarence House in 1949 they received a generous £50,000 government grant to do up the property – much to the annoyance of some Labour MPs who, in an echo of today’s woes, thought the money could have been better spent on austerity Britain. There was a similar kerfuffle in 1963 when Princess Margaret and Lord Snowdon received £80,000 of public funds to renovate their new apartment in Kensington Palace, with mod cons including a sunbed room and a dog-washing room.

Some suggest that the Duke and Duchess of Sussex want to deck out their new place with luxuries such as sprung floors and sophisticated eco-heating systems. But one reason why the costs are much greater for today’s royals is security. Frogmore Cottage has had to be fitted out with the latest electronic surveillance equipment as well as premises for their personal protection officers. It would have been simpler and cheaper if the Sussexes had remained in Kensington Palace where dozens of royals (including William and Kate) are protected within a single compound.

But if Harry and Meghan insist on having a place of their own, shouldn’t they make a larger contribution to the makeover costs? They are certainly not short of liquid assets. Harry inherited £7m from his mother’s estate and is also thought to benefit from a multimillion trust fund set up by the Queen Mother. Having been a successful TV actress, Meghan brings to the table her own private wealth.

The royal couple also get considerable financial support from the Prince of Wales. We learned from the latest financial results that in 2018-19 Charles set aside about £5m from his Duchy of Cornwall revenues for “funding the activities” of both the Sussexes and the Cambridges. Most of those activities are their public duties but it is now admitted that some of the money also goes on private expenditure – such as last year’s Windsor wedding.

Profits from Charles’s ancestral estate have trebled since the millennium, reaching more than £21m this year and allowing him to increase the amount of money going to his two sons by £1.5m in the past two years. So, if he is so flush with cash, why can’t he pay for more of the refurbishing work?

No one is suggesting that all of the renovation costs should be privately funded since by convention royal properties occupied by senior family members are maintained by the public grant – but at a time when the country is struggling with austerity and facing an uncertain economic post-Brexit future, it would be a welcome gesture if the Windsors used some of their own vast wealth to ensure that the royal couple have a roof over their heads. And if a little money could be found from the Duchy of Cornwall, that would certainly be an original idea.

• David McClure is the author of Royal Legacy