In the 1991 John Goodman comedy King Ralph, truly the most important work of art to grapple with what it would mean if an American joined the British royal family, the movie comes to the conclusion that a friendly American is exactly what the royals need to make them bearable. Some Brits, of course, resist this idea: “It’s an unmitigated catastrophe – this song and dance man from the colonies!” wails John Hurt to Peter O’Toole. (It is possible neither Hurt nor O’Toole considered King Ralph to be their finest hour)

In the run-up to Prince Harry’s wedding to Meghan Markle, a song and dance American, the focus was entirely on what her arrival meant. And no surprise, given she is – in order of importance, in regards to her alliance with the House of Windsor – a mixed race American divorcee actress. But this always was a marriage of two narratives. It’s just that hers was so extraordinary that his, amazingly, was briefly put in the shade.

Anyone tempted to underestimate how astonishing it is that a mixed-race woman is marrying into the royal family was duly set right last December when Princess Michael decided that the perfect accessory to sport to a lunch welcoming Markle to the family was a blackamoor pin. We are barely a breath away from when outright racism was very much the norm among the royals, from the Queen Mother talking blithely about “blackamoors” to Prince Harry himself using terms such as “Paki” and “raghead”. And in that regard, there is no doubt the Windsors need Markle a lot more than she needs them.

“I’ve come to Windsor because it’s a mixed-race wedding. I felt no affinity to the royal family before. Now I feel more of a connection to them and this country. And if she makes some of the other royals or whoever feel uncomfortable, well, that’s disappointing, but it’s also gratifying because I feel like, well, now it’s YOUR turn to feel uncomfortable,” Susan Botros, an Egyptian-Guyanese from London, told me at Windsor train station, a stray piece of confetti still in her hair.

Facebook Twitter Pinterest Prince Harry and Meghan Markle stand together at the altar in St George’s Chapel, Windsor Castle. Photograph: Dominic Lipinski/AFP/Getty Images

An article in the New York Times this week looked at how Markle’s American-ness will affect the House of Windsor (headline: “I’m American. I hug.”) Markle’s American friends spoke eagerly about how she will be “an agent of change” for the royals, perhaps because they were too young, or too far away, to recall how things worked out for the last woman who tried to change The Firm. The Brits, however, remember all too well. Piers Morgan, who seems to have managed to convince Americans he is an expert on the royals, predicted she would “chafe” at the various rules imposed on her. Morgan also popped up on Fox News, reminiscing about the time he met Markle for a drink in the pub. “There was a moment when she started looking at her phone,” he began, an opener to a namedropping anecdote which definitely comes at the “oh mate” end of the spectrum. “That was almost certainly Prince Harry,” he decided, retrospectively.

Dickie Arbiter, the Queen’s former press secretary but still ever-ready with a quote for the media, went even further, foreseeing disaster in Markle’s fondness for expressing an occasional opinion: “That’s why Charles I had his head chopped off.”

Play Video 1:23 Duke and Duchess of Sussex depart in Jaguar for wedding reception – video

Welcome to Britain, Meghan!

It is a British tradition for the media to celebrate an upcoming royal wedding by trashing the incoming in-laws, from Diana’s stepmother, Raine Spencer, to Kate Middleton’s Uncle Gary and his memorably named Ibizan villa, Maison de Bang Bang. And sure, we can talk all day about the blatant snobbery behind this trashing. But by any measure, the Markle family gave the press plenty to work with.

The Markle debacles dominated the weeks leading up to the wedding, from her father being caught posing for pap photos to her half-siblings alternately trashing Markle and then complaining she hadn’t invited them to the wedding. Much shock was expressed in the British press about the Palace’s utter failure to control the Markles and the Markles’ lack of etiquette. But thinking British decorum and the Palace press office could hold back an American craving for celebrity and tmz.com is like sending gentlemen on horseback to do battle in drone warfare. And while one can feel rather sorry for Markle and her father that they didn’t get to walk down the aisle together, one can simultaneously note that he continued, even after his much-discussed humiliation, to feed updates on his health to TMZ.com. (Ultimately, all this nonsense was swept away by lovely Doria Ragland, Markle’s mother, the only member of her family who wasn’t exploiting her and therefore the only one to get an invite.)

And so, by early Saturday morning, the talk for so long had been about Markle’s ethnicity, her nationality and her family that it was easy to forget that this was also about Harry. Which is pretty incredible, given that he was the last unfinished storyline of a saga that has become such a part of the national consciousness over the past four decades it feels less like history and more like a myth.

Facebook Twitter Pinterest Well-wishers watch a giant screen broadcasting the wedding ceremony of Prince Harry and Meghan Markle in Windsor. Photograph: Tolga Akmen/AFP/Getty Images

When the wedding started I found a spot near Windsor Castle’s entrance, where I could watch the ceremony on a big screen. People who line the roads at weddings are, by definition, the most die-hard royalists, and all the usual figures were out in force: the men bellowing and ringing bells in the hope of convincing a passing American TV crew they are an actual town crier; the men in suits made of Union Jacks. Everyone I spoke to had waved flags at Prince William and Kate Middleton’s wedding, had camped out for Diana’s funeral and, in some cases, her ill-fated wedding. (No one mentioned going to Prince Andrew and Sarah Ferguson’s now all-but forgotten wedding, and yet the awkward truth is that Harry and Meghan’s marriage is no more significant than that one was, in terms of lineage.) Not being a royalist of any stripe, I’d not been to any of those. In fact, there was only one royal gathering I’d gone to in person: Kensington Palace, the day after Diana died.

The death of Diana and its fallout is the story which the royal family has only just recovered from, barely, and it is the last royal story I cared about at all. I was 19 at the time and in my mind’s eye Harry will always be the little 12-year-old boy in the too-large suit walking in his mother’s funeral procession, stared at by a billion strangers, swathed in privilege but now stripped of affection and warmth. I’d always found the royals a cold proposition, Diana excepted, but the sight of that little boy, his head bent, not daring to look up at his mother’s coffin in front of him was, and remains, genuinely heartbreaking.

What was going to happen to this cheeky boy, suddenly deprived of his fun-loving mother, and left with his cold father who barely touched him at her funeral? For a long time – a Nazi uniform here, a game of strip billiards there – it looked like the answer was: nothing good. It looked like he was losing all that had been good about his mother, and was morphing into all that is bad about the Windsors.

But then, things changed. He found causes he cared about. He stopped resenting the responsibilities that came with the privilege he’d always enjoyed. He also started talking about mental health issues, a conversation his mother began 30 years ago.

Not since Harry made that awful walk 21 years ago has he been watched by as many people at once as he was at his wedding, and it would take a stonier hearted republican than me not to have felt something at seeing how that sad and lost little boy is now such a happy man. Many could say that his mother’s spirit was represented by the presence of Elton John at his wedding, and that’s true. But a more fun representation of it to me was him appearing to mutter to Markle at the altar “I’m shitting it” and then giggling, in front of millions of people.

I saw some snarking online about Bishop Michael Curry’s passionate sermon, and certainly the royal family seemed unnerved by it, with Zara Philips watching it in apparent open-mouthed shock and Kate and Camilla shooting each other some heavy side-eye. But as I watched the bishop refer to love, emphatically and repeatedly, not hurriedly rushing over the word as is more traditional in royal and, to be honest, English weddings, I thought, well, maybe this is what Harry needs after all, this kind of corrective. Enough English coldness, bring on American demonstrativeness – it was what his mother had strived for, after all.

Play Video 2:02 US minister Michael Curry captures world's attention with powerful royal wedding sermon - video

The day before the wedding, when it was announced that Prince Charles would walk Markle down the aisle, instead of her mother or one of her friends, it looked like The Firm had asserted itself against any potential for change Markle might bring. But the inclusivity and diversity of the ceremony refuted that, and it could only have been Harry who ensured that would be the case. Against all odds, Diana’s boys have grown up OK, and as embarrassing as the monarchy is as an institution, they themselves are not embarrassments. Harry in particular may well be genuinely good for this country, thanks to Markle. It turns out King Ralph was right: what the royals needed all along was an American.