Kate, Duchess of Cambridge, leaves BAFTA, after she delivered a speech to launch the "Taking Action On Addiction" campaign, in London, on Tuesday. Photo / AP
OPINION:
In 2017, in what would ultimately prove to be his final official engagement before retiring from official duty, Prince Philip quipped he was "the world's most experienced plaque unveiler".
Like the best jokes, this one contained a savage kernel of truth: The day-to-day of what many of the working members of the royal family do has not substantially changed since Philip joined the firm in 1947. Wave, shake hands, pull back a tiny velvet curtain, return to Bentley. Repeat ad infinitum.
This was a model that was never going to work for Diana, Princess of Wales, who saw the potential to play a much more engaged and deeply human role in public life than being another plaque unveiler extraordinaire.
What Diana pioneered, aside from pie-frill collars and the royal TV tell-all, was a version of work built on helping those most marginalised and forgotten by society, turning hugging into a power move along the way.
If ever there was a question about whether that legacy lives on, then look no further than events overnight in London where her daughter-in-law Kate, the Duchess of Cambridge, delivered a landmark speech about addiction.
Standing at the lectern, dressed in dazzling red, never has the resemblance to her mother-in-law been more pronounced.
"No one chooses to become an addict, but it can happen to any one of us," the 39-year-old told the audience, saying that she wanted to break the "taboo and shame" that surrounds the issue in a positively Dianaesque turn.
Later, in an unscripted moment, the royal came face-to-face with I'm A Celebrity TV hosts Ant and Dec at the Bafta headquarters where the trio had a soul-baring chat.
"The more you speak to everybody … and hearing some of their stories today … once you start sharing your story there are so many people who have experienced it themselves, or have known someone," Kate said.
Ant, who has previously battled drug and alcohol problems, told the royal he had "felt that myself. By the time I asked for help, it was bad. But as soon as you open up to people … the problems start to disappear. It gets better."
That the next Queen of the United Kingdom was standing around a corridor having such a deeply personal tete-a-tete about such deeply personal issue shows just how powerful Diana's impact on the royal house is to this day.
Diana's career was characterised by a dogged commitment to dragging ostensibly unpalatable and awkward topics into the light. She innately understood that the lofty heights of royalty provided the perfect perch from which to engage in a spot of societal stigma-busting.
An HRH, Diana worked out, could be used to the greatest effect by helping those most marginalised, from shaking hands and hugging Aids and leprosy patients to visiting homeless shelters with her sons Princes William and Harry to speaking about eating disorders.
That lesson is one that Kate has very clearly paid attention to.
While her initial years as a member of the house of Windsor were dogged by what looked suspiciously like a certain indifference to the rise and grind dreariness of royal life, what we have seen of late is the Duchess truly coming into her own and using her platform to potent effect.
Never have so many floral dresses and nude pumps given so much.
Over the course of the last 24 months, Kate designed a garden for the Chelsea Flower Show with the aim of encouraging parents and kids to get outside; launched her landmark 5 Big Questions early childhood survey which saw more than 500,000 British parents take part, and establish a comforting and ubiquitous Zoom presence during the pandemic.
We have also seen her appear – and speak – much more frequently in public.
What has become increasingly clear, and especially in recent weeks, is that while Kate might have taken her time to find her feet as a working HRH (and might have taken one too many trips to Mustique), she is now very much setting her own agenda.
Kate's bouncy blow-dry and big smiles belie that, behind the scenes, she is up to something more far-reaching and with much greater societal heft than simply being a fragrant, photogenic addition to the house of Windsor.
However, here is where Kate's story leaps off from that of Diana.
What is fascinating is that in retrospect, everything the princess achieved was despite the disapproving royal house who viewed her popularity and radically human approach as a direct threat to the monarchy.
Instead, Kate has managed to accomplish, right in front of our very eyes, something which Diana never could: She has managed to build her own power base without upsetting the palace ecosystem. Somehow, she has established a constituency without getting anyone's pinstriped hackles up.
What makes Kate such a formidable figure going forward is that not only is she clearly driven by the same fire and drive to help those less fortunate as Diana was, but that she is doing it with support from the very top.
(There's a reason the Queen bestowed on her granddaughter-in-law the honour of making her a Dame Grand Cross of the Royal Victorian Order for services to the sovereign in appreciation for her work. Well that and producing an heir and two appropriate spares maybe too …)
The timing of Kate's speech is also significant, coming on the very same day the Queen, Prince Charles and Prince William were welcoming 120 world leaders to Windsor Castle. This overlap would not have happened if Her Majesty and the powers that be had not approved.
Diana might have essentially staged a stealthy coup, redefining and expanding the scope of what a working member of the royal family could talk about in the public sphere, but gone are all the harrumphing courtiers who were perpetually galled by the intractable young princess' moxie and dedication to uncomfortable causes.
Kate might have inherited various priceless items from Diana, like her Ballon Bleu Cartier watch and enough sapphire jewellery to make Cartier jealous, but the most precious legacy might be the one we are seeing the Duchess embrace right now.
Thanks to the Princess, being a future Queen now carries with it the possibility to play an active role in public life and with not a plaque in sight.
• Daniela Elser is a royal expert and a writer with more than 15 years experience working with a number of Australia's leading media titles.