The first imitation I ever saw of Diana, Princess of Wales was in my bedroom when I was five. It was a Diana Bride doll, ordered by my mother from a catalogue, although with her rictus smile and huge helmet of hair she looked more like Nancy Reagan. The details didn’t matter: she had the vague outlines of princess – big glittery jewels, big glittery eyes – so I could project whatever I wanted on to her, and I did; I played with her so much I snapped off her right foot.

This is a true story, but if the metaphor within it feels too heavy-handed, then I would advise you to keep clear of the many films and TV shows about Diana, none of which shy away from the obvious metaphorical nudge and shove. In his eulogy for his sister at her funeral in 1997, Earl Spencer described her as “the most hunted person of the modern age”. Screenwriters since have taken that description and run pell-mell with it: in the last season of The Crown, she was a beautiful stag; in Spencer – the new film by Pablo Larraín, starring Kristen Stewart as Diana – she is a pheasant, “beautiful but not very bright”, as she sighs sadly. Both the stag and pheasant are, of course, hunted by the evil Windsors, because that has been the narrative around Diana ever since her death, even though not even the Daily Express still believes they actually killed her.

Ever since the Windsors saw in young Diana Spencer the vague outlines of a princess, the world has projected on to her whatever it wanted. An unworldly and barely educated Sloane who was married off at 20, she offered a conveniently blank canvas in her lifetime and even more of one afterwards. Was she a saint or a manipulator, a schemer or an airhead? Does the story of Diana tell us something about the royals? Women? Celebrity? Britain? Pick and choose, folks!

Back in the 80s, when Diana first became a public figure, that other great no-surname-necessary female celebrity, Madonna, was explicitly comparing herself to Marilyn Monroe, but she always had too much personality, confidence and autonomy to fill that role credibly. As Elton John realised when he quickly repurposed his song Candle in the Wind for her funeral, Diana was the real Monroe of the second half of the 20th century: photographed so frequently she seemed more like an image than a person, and she learned to exploit her own appearance as much as the media did. Then suddenly, that perennial little girl lost was lost for good, in a plot twist even her step-grandmother, Barbara Cartland, would have rejected as too OTT. Like Monroe, Diana was only 36 when she died.

That quality of vagueness around Diana makes her a tempting subject for a certain kind of film-maker, but it also makes her impossible for an actor to capture. I am a great fan of camp absurdity, so years before Naomi Watts simpered her way through the widely panned 2013 film Diana, I watched the 2007 US television movie, Diana: Last Days of a Princess. Now, Diana: Last Days of a Princess requires several leaps of belief, not least of which is its entire plot, predicated on the idea that Diana and Dodi Fayed was the great love affair of the 20th century.

Patrick Baladi – best known as Neil from The Office – is, even less credibly, cast as Fayed, presumably in an attempt to make the never wildly appealing Dodi somewhat sympathetic. Yet it is Genevieve O’Reilly who really has the tough job here, having to thread the needle of conveying a brilliant, selfless, caring saint who just happens to be spending the summer on the Fayed yacht. Screenwriters love to talk about how much they like to write “complicated women”, by which they mean a female character who sometimes gets a bit cross and maybe doesn’t always have blow-dried hair. They don’t mean a woman who is caring and manipulative, kind and shallow. Such women – as the Windsors discovered to their eternal misfortune – are just too much for some to handle.

Diana’s blankness means film-makers can do what they like with her life, so in the past 12 months, it has been rendered as a musical (Netflix’s Diana: The Musical, starring Jeanna de Waal), a gothic fable (Spencer) and a traditional biopic (The Crown, whose most recent series starred Emma Corrin as a younger Diana, with Elizabeth Debicki taking over for next year’s fifth outing). I haven’t seen Debicki’s portrayal yet, but it is to Corrin’s enormous credit that her naturalistic portrayal of Diana in the previous series never seemed ridiculous. Because, really, the further we get from Diana, the more tragically ridiculous her life seems. How else to tell the story of this young girl dragooned into an absurd family, which is then almost undone by her, other than as camp or horror? Never has The Crown’s slow-paced, minutely detailed format seemed more fortuitous than in its telling of Diana; whereas the Queen doesn’t change, really, from her teenage years to grandmotherhood, Diana’s shift from childlike virgin to vengeful shagger of the Hurlingham Club makes a lot more sense in a story that doesn’t try to capture her life in 90 minutes.

But The Crown fudges the truth in suggesting that Diana was bewildered by life in the palace, because, really, she was a normal person, as proved by her fondness for Duran Duran. So we are encouraged to imagine how we, fellow normal people, would have felt if we were living in Buckingham Palace and assume that’s how she felt, too. Of course, it is precisely because Diana, the daughter of an earl, was nothing like any of us that she was deemed suitable to marry Prince Charles. The one part of royal life that would have been unfamiliar to her was celebrity, and that was the one part she liked. It is fair to suggest, as The Crown does, that Diana needed love from the crowds because Charles denied her any; it’s equally fair to suspect that Diana also just really liked attention. But the latter doesn’t fit within the perennial good (Diana) v bad (the royals) narratives around this saga.

These black-and-white outlines make Diana’s life more suited to a musical, so Diana: The Musical is something of a heartbreaking missed opportunity. Unlike apparently everyone else, I rather enjoyed its doggerel lyrics (“Darling I’m holding our son / So let me say jolly well done!”) because, let’s be honest, Diana was always more of an Andrew Lloyd Webber girl than a Stephen Sondheim devotee, so the form suits the subject. But as both The Crown and Spencer take pains to emphasise, her favourite musical was The Phantom of the Opera, and Diana: The Musical desperately needs some of that show’s camp and schlock. Instead, it is a weirdly straight faced, adoring show about a princess. Even the royals are treated with far more moderation than they deserve, with Charles coming across more like Hugh Grant than the cold-hearted manchild he seems to be. Seriously, how can anyone make a musical about Diana and not include a song in which the future king is recorded wishing he was a tampon?

Spencer has a lot going for it: it looks great and the premise is amusing, with Diana as a kind of Mrs Rochester figure being driven mad by her cold husband (Jack Farthing) and a cruel servant (Timothy Spall, nostrils constantly flared). For some reason, Stewart plays Diana as if she were permanently being interviewed by Martin Bashir, all furtive meaningful side-glances and pointed muttered asides. After two hours of this, she comes across as not so much mad as peevish.

It doesn’t help that she is constantly moaning to the servants about how hard done by she is, while they dress her, cook for her and clean for her. Not even the omnipresent menacing music by Jonny Greenwood can make being summoned for dinner seem quite as abusive as we’re apparently meant to find it. Check your privilege, Lady Di! Maybe it’s because Prince Harry has spent the past two years going on about his miserable life while still enjoying all the privileges that life has to offer, but the whole gilded cage shtick feels a lot less interesting than the prison that was, clearly, Diana and Charles’s actual marriage.

The story of Diana is now so well known it is verging on legend, and legends are only worth retelling if there is something new to say that has the unmistakable feel of truth. The Crown, with its judiciously loose approach to history, has, improbably, found plenty to say about this overtold story; Diana: The Musical has nothing to say beyond that someone called Diana once married a prince (not news). The one moment when Spencer really sang for me is – semi-spoiler – the scene in which Diana introduces her children to the joys of Mike and the Mechanics. It’s fun, it’s silly, it’s sweet, it’s shallow, it’s irresistible. It’s Diana.

Spencer is in cinemas from 5 November.