01/08/2017 12:24 BST | Updated 02/08/2017 06:11 BST

Diana's Tapes - When Does The Past Become History?

Ian Waldie / Reuters

It's the topic of the day - whether or not Channel 4 should broadcast the tapes the late Diana, Princess of Wales, recorded with her voice coach Peter Settelen. Speak of it on social media -never mind on the BBC - and you get a storm of comment, with opinion divided surprisingly evenly. The answer may be no, they shouldn't - but that's quite a strange thing for a historian to say.

After all, any writer of history spends their life rummaging, so to speak, in the lingerie drawer. Scouring the private letters and diaries of famous people for revealing details, and then passing them on to as many readers as possible. But this is different - isn't it? Can we be quite sure of that, actually?

The waters here are pretty muddied, and not only by the fact some of the material has long been available after airing in the USA. Muddied recently by the laudable decision of Princes William and Harry to speak out about the past, and their pain, in support of their mental health charity. Muddied a quarter of a century ago by Princess Diana's own decision to speak very publically about her problems - but that word 'publically' may be the key. These tapes are not the Panorama interview Part II. They were made in the expectation of privacy. And the Princes' past is theirs to discuss. Should that mean the rest of us can trample through it quite freely?

Of course up to a point the past of the Royal Family is the whole nation's property. It's why they're supported by our taxes, basically. But where should that point come, precisely? The line has been constantly redrawn over the past century. Diana's adult life saw a time of maximum press and paparazzi intrusion - now replaced by the public with their smart phones and their social media. The royals of the earlier twentieth century (though not necessarily the more distant past!) were allowed to conduct far more of their lives in decent privacy.

There are strong indications that the next generation will seek to turn back the clock to some degree. Prince William with his young family - Prince Harry with his girlfriend - expect to step out onto the stage to give the public their due, and then step back into the wings, and a different identity. It's arguable artefacts from the Diana age belong to that age, not to this, and should be treated accordingly... But that is to evade the larger questions around the Settelen story.

One question is of the public's need to know, and it is hard to feel that broadcast of these tapes serves the public interest in the best sense of the term. We may, pruriently, like to know about Diana's sexual relationship with Prince Charles. But do we need to know, really? It's different to, for example, that other recent question of whether the href="" target="_hplink">Duke of Windsor had links with the Nazis.

If you accept that we need to understand our history to avoid repeating it, then it's surely important we understand all its complexity. And the fact that 1930s Britain saw broad panorama of opinion about Nazi Germany really is part of all our story, not just the story of one family.

But the question of public interest is itself a possible trap. We wouldn't want Palace officials to determine that, would we? Or the representatives of any political party? Maybe we will have to fall back on something more impartial - like chronology. It's 20 years since Diana died. And maybe we need to codify not just what we can reasonably expect from our royals (or indeed from any other celebrities). We may need to decide just when the past does become history.

It's picking a figure out of the air, but - some 70 years, maybe? Three score years and ten no longer describes the average first world lifespan, but it's long enough that everyone personally touched by a story like this is likely to have moved on in one or another way.

Such a timescale would still allow us to explore the Duke of Windsor's story. But, after a mere 20 years, the legend above Diana's grave could still read R.I.P.