For a long time, we didn’t know much about Frogmore Cottage, the newly refurbished home of the Duke and Duchess of Sussex — but all that changed this week when the 100-page Sovereign Grant report, which details every cent of taxpayer money the royals spent the previous year, was released.

Deep in the largely mundane papers was a fact that made headlines around the world — the huge renovation was mostly paid for using $4.3 million of the UK taxpayers’ money.

Reaction to this particular uncomfortable truth has been swift and brutal. British commentators have been up-in-arms the wealthy young couple did not use their own private fortunes to pay for the conversion of the dilapidated property in Windsor into a smart, modern home. (The Sussexes have paid for fittings and fixtures and are said to have spent about $450,000 of their own dosh on that.)

According to a poll done this week by Good Morning Britain, 87 per cent of respondents thought the taxpayer shouldn’t have been made to fork out for the Frogmore renovations. Royal commentator Robert Jobson tweeted there were “calls for a full parliamentary inquiry into royal spending after the release of the accounts”.

For Harry and Meghan, who are fashioning themselves into global activists, this lavish lifestyle enjoyed on someone else’s dime seems to undermine the sincerity of their campaigning, with some calling it their “biggest mistake yet”. (Supporting veterans has been a key cause of Harry’s. Republic.org CEO Graeme Smith pointed out on Twitter the Sussexes’ Frogmore bill was equal to the cost of building a centre to help returning royal marines suffering from PTSD.)

This might sound like a storm in a cup of Earl Grey, but the future of the royal family is predicated on the continuing benign acceptance by the British people.

Facing significant political instability (the jostling to assume the UK prime ministership continues) and teetering on the edge of a catastrophic Brexit, seemingly extravagant spending by a group of people who don’t have to put in a full 40 hours every week is understandably galling to many Brits.

For the Duke and Duchess, they are getting perilously close towards entering the danger zone — that is, dramatically losing public approval. It has already been a bruising year for their public image, from the former Suits star’s highly controversial six-figure New York baby shower to their decision to keep the media in the dark about their son’s arrival, to then eschewing the usual mass media call.

Boisterous, cheeky Harry has always held a special place in the hearts of Britons, but that affection and the latitude that comes with it are finite.

He and Meghan reportedly have plans of becoming roving, international ambassadors, however the global adoration they enjoy will be substantially undermined if they are perceived at home as Marie Antoinette-esque figures who just happen to be handy with a hash tag.

Because if there’s one thing the royal family is keenly aware of, it is perception is everything.

In 2008, during the GFC, the Queen was said to be concerned Prince William’s girlfriend Kate Middleton seemed to spend her time popping off on jolly jaunts to ski or top up her tan in Mustique. Sensitive to Her Majesty’s suggestion, Kate went off and found herself a charity to join, quick sticks. While the Queen might spend $726,000-a-year on booze, she is keenly sensitive to the prevailing public winds.

Late last year, Prince Harry nabbed the number one spot in a YouGov poll of most popular royals, with 77 per cent of those polled hailing the Invictus founder as their favourite Windsor. The Queen came in second and the Duke and Duchess of Cambridge third and fourth. Yet as of today, Harry has slipped into second position. Sure, that is not a huge drop, but this sort of downward trajectory sets a worrying precedent.

Prince Harry is worth about $54.4 million (thanks to inheritances from Diana and the Queen Mother), while Meghan reportedly has about $6.9 million in private wealth, according to the Evening Standard.

In hindsight it seems stupefying they didn’t predict the public reaction to letting Crown funds pay for their Frogmore move, and in coming months, with a disgruntled public and a PR war to fight on multiple fronts, not putting their hands in their own pockets might seem like a false economy.

Daniela Elser is a royal expert and freelance writer. Continue the conversation @DanielaElser