The last time I spoke to Princess Diana was 21 years ago, and we were both having a pretty awful day.
I was hand-delivering my letter of resignation as her private secretary, and she was adjusting to the news that her beleaguered support organisation was about to have a tedious vacancy at the top.
Not only was this highly inconvenient, but it also broke a cardinal rule of royal employment: such vacancies should only occur with the prior approval of the royal employer.
Instead, I had had the temerity to resign, without her consent, and she hadn't even had the fun of firing me first.
No wonder I felt a death ray being aimed at me from the famous blue eyes.
Even as I tried to meet it head on, I reflected on the stupidity (or was it arrogance?) of those who forgot the ice and steel programmed deep into the aristocratic DNA of Lady Diana Spencer.
But then, as she took the envelope, I thought I saw the look in her eyes soften.
I might have been, at that moment, a candidate for instant execution, but there had been many other moments – almost eight years of them – when I had been a loyal, useful and even indispensable accomplice in what had been a wild ride through the royal universe.
By chance and also by choice I had been strapped into the rocket ship with her. But now the thrills were too few, the gyrations too giddy and our once-soaring flight path seemed to be headed inexorably earthwards. I wanted off.
Yet even then, as we awkwardly shook hands in farewell, the look she gave me stirred a familiar protective reflex that has only grown with the years since her high-flying odyssey came to such a catastrophic end.
'The end of the fairy tale' is a phrase too often used glibly to describe the failure of the Prince of Wales's first marriage. While the wedding in 1981 had many of the elements of a fairy story (the Archbishop of Canterbury used the words during the ceremony), the sequence of events begun that day in St Paul's had a horror-story ending in the Alma tunnel in Paris.
And as we have heard from all the main protagonists, any Disney-type magic was in very short supply from beginning to end.
Disturbingly, in its place, a far more pernicious fantasy has been cultivated. It has suited many critics to have us believe, in the words of Penny Junor, the Duchess of Cornwall's biographer, that Diana was 'an injured soul, a poor damaged creature who needed help'.
To support this convenient assertion, a systematic attempt has been made to have the Princess remembered as the pathetic possessor of a personality disorder, incapable of royal duty and an impossible burden on her stoic husband.
Even allowing them credit for some poodle patriotic motive, those responsible for this campaign seem to have cared little for the feelings of her sons, and even less for the ethics of publicising a diagnosis of someone unable to answer back – and without the tiresome formality of clinical examination.
Consider instead the possibility that the fairy tale ended for some far simpler and depressingly mundane reasons: adultery, jealousy, neglect and deceit prominent among them.
It was Diana's determination not to be discarded as an inconvenient mistake, but instead to take on her critics and beat them at the royal game, that provoked a panicky attempt to persuade the world that she should be diminished, marginalised and, if possible, forgotten.
One has only to ask who benefits from such political-style spin to understand the damage it does to a revered institution like the monarchy, which commands a loyalty no politician dare claim.
All the more credit, then, to her sons for, it seems, awakening to their opportunity to protect their mother's true legacy.
In their own words "the time is right to remember her positive impact", and in last month's beautiful and heart-warming documentary they made their own incontestable tribute to her achievements, not least as a loving parent.
Perhaps even more significant was their recognition of her role as mentor in the authentic emotional engagement that a new generation of monarchists – like it or not – hope to find in their ruling family.
To such moving personal memories, a fuller portrait of the Princess would add some distinctly public achievements too.
Diana as mother is an image that might soften a stony heart, and Diana as global charitable icon might impress a sceptical one.
But the memories that some hearts should find unsettling – an unease that perhaps explains why they've been all but eradicated – are those of Diana doing her constitutional duty as queen-in-waiting.
Luckily for me, I witnessed many of these at first hand. I accompanied her to one-on-one meetings with heads of state and of government from Buenos Aires to Tokyo, Washington to Moscow, Paris to Cairo, Islamabad and Harare.
As they posed for photographs with the statuesque advocate for so many of the world's least-fashionable causes, these leaders somehow seemed unaware of her status as a poor damaged creature.
And not one would have questioned her aptitude or capacity for diplomatic duties she fulfilled with unfailing grace and good humour.
No sign either of this damaged creature as, still younger than Harry is now, she donned combat fatigues to visit one of her regiments on operations in Northern Ireland; or faced down a baying mob of CND protesters to christen a Trident nuclear missile submarine; or navigated the corridors of power in Brussels and Geneva in support of causes – not least British trade – for which she was a seasoned asset and campaigner.
So let those who continue to question her sanity ponder this instead: that the injured soul who comforted lepers, hugged babies with Aids or visited the criminally insane, perhaps understood better than most the courage needed to acknowledge one's own frailties.
Worth bearing in mind, the next time you encounter disdain directed at Diana, the media manipulator, the temperamental inadequate or cheerleader of the emotionally incontinent.
Such thoughts and many more were jostling in my mind as I trudged away from Kensington Palace that awful day, two decades ago, the reproach in those blue eyes still burning.
It burns today, never more than when Diana's alleged failings are co-opted to serve the latest artful raid on our benign loyalty.
As we look back in gratitude, we should also look forward with concern for the kind of monarchy we want. In considering the answer, the late Princess of Wales's experience is more than just an enduring example: it is also a warning of what happens when royalty and decency become irretrievably estranged.