Which previous royal crisis does the current one most closely resemble? Given the reflexive British response to any royal drama, it was no time before crack monarchy experts identified the incredible similarities between the abdication of Edward VIII and an overdue realisation by the constitutionally insignificant Sussexes that palace life is unlikely to suit anyone independent and talented, especially when racism intensifies those twin deterrents – the Queen’s household and the British press. Don’t both events feature US divorcees, separated only by 84 years and racial difference? Snap.

If only the similarities had been spotted sooner and warnings issued. For what psychic could possibly have predicted, having read Meghan Markle’s blog, or seen footage of her, aged 11, condemning sexist TV ads, that she might not submit as readily as her otherwise unemployable in-laws, Camilla, Duchess of Cornwall, and Kate, Duchess of Cambridge, to a career principally composed, for its lead female members, of dutiful handshaking and smirking? Or guessed how very quickly this occupation might pall if, unlike Camilla, Kate and, indeed, Prince Andrew, Meghan were simultaneously to find herself stalked by obsessed celebrity-commentators, some of them partnering in this experiment with estranged members of her own family?

If Meghan never, unlike Diana, Princess of Wales, had to run from photographers, she has been subjected, courtesy in particular of the Daily Mail, to a new, permissible variation on press harassment: relentless, condescending censure informed by what 70 female MPs recently described as “outdated, colonial undertones”. One day, a reprimand might focus on Meghan’s relationship with her father, another on her tights, her friends, her “bump-boasting”, her extravagance, her ruthlessness, her unhappy staff, her christening photographs, her meanness to Kate. Not forgetting her Vogue editing, chapel dissing, Queen snubbing, baby showering, baby holding, baby hiding and Harry controlling. In the light of this trolling, the press’s earlier pursuit of Diana practically radiates mutual respect.

Among alternatives to the abdication, the Sussex crisis has been compared to Diana’s unexpected decision in 1993 – shortly after the Sunday Mirror published illicit gym photographs of her on her back, in a leotard – to retreat, as it turned out temporarily, from public duties. After much private rehearsal, she delivered a speech that was, according to her disapproving private secretary, Patrick Jephson, “fundamentally dishonest”. “I hope you can find it in your hearts to understand and to give me the time and space that has been lacking in recent years.” The royal household had been alerted but only thanks to Jephson: “Unknown to my boss, I had written a briefing note for the Queen herself.” Colleagues were to expect a “tearful and very public withdrawal”, which, he writes in his heavily disdainful memoir, “appealed to the martyr, the emotionally deprived child and the showgirl within her”.

Not having been around – quite – long enough for the abdication, but lucky enough to witness, as a Guardian reporter, Diana’s sublime performance in 1993, I’m more struck by the big difference between that and the Sussexes’ exit: the civility the princess received from her customary persecutors. She had, to media dismay, already delivered one major shock, Andrew Morton’s book, with which she initially denied any connection.

Technically, like the Sussexes, the kind-of departing princess was letting down the Queen, occupying a free palace, sponging off taxpayers, had carefully “plotted” her escape – but had no thought of “working to become” financially independent. Jephson thought she was, in the phrase currently popular with disapproving republicans and disapproving royalists alike, “having her cake and eating it”. And yet instead of asking something such as “Who the f**k do they think they are?”, the Mail announced: “Charles Drove Her To It.” “Early reports,” Jephson wrote, “were of uncritical understanding and sympathy.”

Why the hostility? Who knows. Why did Iago hate the Moor?

But when it came to Diana’s son and his wife, early reports abounded in name-calling and derision, principally from the voices whose sustained, seemingly visceral enmity has contributed to the Sussexes’ unhappiness. Or to summarise these rebukes, in the new loyalty-sanctioned argot of the Daily Mail: how dare you fucking escape, you fucking bastards?

Why the hostility? Who knows. Why did Iago hate the Moor? Claims about reckless constitutional damage have proved, however, a convenient front for motiveless malignity.

The proposal that the Sussex exit, however inconvenient or half-baked, endangers the monarchy should, again, be compared to the serial jolts of the Diana years, also featuring Charles’s Camillagate adventures, the princess’s Panorama interview, Fayed freebies and a heartlessly misjudged funeral procession, from all of which the extended dependent family emerged prosperously intact.

More topically, the Sussex announcement is arguably less of a blow to this cornerstone of the constitution than, say, the crown’s inability to resist manipulation and lies orchestrated by the Downing Street bum-flasher, Dominic Cummings. Even with their failings officially confirmed by Madame Tussauds – where they are expected shortly to reappear in a flickering tableau around Richard III – the Sussexes’ conduct may appear to some subjects less outrageous than Prince Andrew’s. If the Queen felt similar fury or disappointment when she found she’d hosted Jeffrey Epstein and Ghislaine Maxwell, it never reached the press.

Turning to another Epstein associate, we find Sarah Ferguson flogging her new “lifestyle brand”, Sarah Senses, in Riyadh, as a special guest of Prince Mohammed bin Salman. Perhaps, encouragingly for the future of SussexRoyal branded merch, the Saudi-loving duchess has yet to be identified as either a constitutional hazard or a royal disappointment. If anything, the departing Sussexes have surely strengthened the monarchy, not just by accelerating, with this unscheduled purge, the slimming-down demanded both by reformers and Prince Charles.

Sympathy for the spurned Queen is absolute. And nothing, after decades of mutual suspicion, appears to have united the palace and sections of the press like the conviction that mutinous incomers are a greater threat to a monarchy than its longstanding connections with a predatory paedophile. They could both, however, be wrong.

• Catherine Bennett is an Observer columnist