The Crown isn’t making the royal family look bad. They do a fine job of that themselves

Which, below, did the Prince of Wales not say?

a) “I am the Prince of Wales and I will be King!”

b) “I need encouragement and the occasional pat on the back too.”

c) “Darling, come back, of course I want to hug you.”

Any accredited royal writer would know instantly that the answer is b), a line from season 4 of Peter Morgan’s The Crown. The first quote was aimed by a tantruming Charles, along with a book, at Paul Burrell. “I can still see its fluttering pages whirring through the air,” Burrell wrote in A Royal Duty. Quote c) is from The Housekeeper’s Diary by Wendy Berry, a book banned in the UK. “In 1986,” she wrote, “Diana was still making an effort to be loving and affectionate to her husband.”

So, later, which of these words are Morgan’s, not Princess Diana’s?

a) “I hate you, Charles, I fucking hate you.”

b) “I need you. You give me strength. I can’t stand it when I’m away from you.”

c) “I still want to make this marriage work. With all my heart.”

Morgan’s is line c). Quote a) comes from Berry and b) from Love and War, James Hewitt’s memoir of his affair with Diana.

It’s the difficulty, for amateurs, in distinguishing between invented and genuine that explains, according to a succession of royal experts, why Morgan’s dramatisation is more threatening to the royal family than the unlovely material already emerging – thanks to royal experts – in Diana’s lifetime, sometimes with her help.

“People actually do believe it,” said Hugo Vickers, self-styled “royal hierophant”, “because it is well filmed, lavishly produced, well acted with good actors. You can’t just dismiss it as tabloid rubbish.” He finds the series “totally one-sided”.

Fellow Charlesite Penny Junor thinks the dramatisation is over-indebted to Diana. “How easy it is to be seduced,” she writes, “into thinking what we see on screen is what really happened and this is what members of the royal family really said to one another.” Though, equally, how easy it is, when such royal authorities assemble, to forget that some of the deadliest lines – Charles’s “whatever ‘in love’ means” – are verbatim.

Given more concern for royal feelings, it’s true, Morgan probably could have ignored Diana’s first-hand accounts, excluded scenes in which she is isolated or gaslit, and concentrated on Diana-free episodes. Charles’s close friendship with the late Jimmy Savile, for example. Or his devotion to Laurens van der Post, both before and after the late seer was revealed to have sexually exploited – raped – a 14-year-old girl consigned to his care. In the end, anyway, the producers would no doubt have alighted on something both true and appropriately heroic that we have inexplicably forgotten.

Junor is also exercised, like many Telegraph correspondents, about factual errors. The first restaurant in which Camilla met the unwitting Diana was not, for example, Ménage à Trois, but – a key distinction to anyone who knows anything at all about the London restaurant scene of the early 80s – “an Italian restaurant in Pimlico” called La Fontana. “To know Camilla,” Junor adds, by way of confirming her own objectivity, “is to love her.”

Even Lord Spencer, who has done more than most to humble the royal family, says the programmes should come with a health warning. Something like “this isn’t true but it is based around some real events”.

He might have a point. Maybe a prominent warning could once have instilled more suspicion about the wonders of Dominic Cummings, as acted by Benedict Cumberbatch or, in future, remind audiences that dialogue in the thriving new genre of unwarranted and insensitive homicide docudrama is likewise made up, sometimes against the express, anguished wishes of survivors or relations.

But whether it’s out of deference to the royals or to audience size, the ethics of biopics and docudramas have rarely, until The Crown, appeared to be of consuming media interest, even when their subjects were willing to talk. Actually, it’s always possible that some royals feel like Tonya Harding, who wished she really had told a judge, as in the film I Tonya, to “suck my dick”. As it is, we’re left with palace “insider” claims of royal outrage about “fiction presented as fact”.

Since this is the second time in a month (following the Martin Bashir revelations) that royal commentators have felt compelled to move more or less en bloc against an outsider whose methods they deplore, the creation of some sort of organised guild or union is surely overdue. Royal specialists have for years taken sides, but this was always, you gathered, undertaken regretfully, professionally, out of virtually Baghottian reverence for the institution at risk. No passionate Diana or Charles advocate – or adversary – ever intended by their partiality to expose the entire royal family, as The Crown relentlessly does, as cruel, spoilt and silly, essentially a collection of pitiful victims.

Yet, as the insiders’ guild must recognise, this dramatised victimhood means, for some key characters, including Camilla, a definite gain in redeeming qualities. Certainly, her reflections (courtesy of Morgan) on fairytale narratives have a mournful appeal absent from the leaked tampon-themed tape. Similarly, when she speaks Morgan, the late Queen Mother fluently evolves into something more sympathetic than the tipsy, racist old spendthrift whom AN Wilson recalled, at one dinner, ridiculing TS Eliot (“such a gloomy man”).

Reinvented by Morgan and a superb Helena Bonham-Carter, even Princess Margaret acquires an emotional complexity that would be unguessable from an account reliant only on her well-recorded history as an utter nightmare. Waiting pages and footmen, Burrell recorded, were forbidden the telly; returning late, Margaret would check the set for tell-tale heat: “Lilibet, someone has been watching TV!”

More recently, there could scarcely be a more powerful reminder than Prince Andrew’s Newsnight interview, with all his sensitivity towards people still living, of the attractions of artistic licence where verifiable royal reality could look so immeasurably worse.

• Catherine Bennett is an Observer columnist