This weekend's wedding is something of a PR coup for the British royal family, in that it introduces a welcome African American note into a previously whiter-than-white bloodline and nudges the Royal household toward a closer resemblance of the diverse country over which it rules.
But it could not come at a more turbulent time for British race relations.
As the town of Windsor undergoes its obligatory pre-nuptial primping and the nation opens its arms to an American woman of colour, British politics is grappling with an ugly immigration scandal that has seen black Britons deported, raising claims that Britishness is still, at heart, a pretty pale affair.
Home Secretary Sajid Javid this week confirmed that 63 members of the "Windrush Generation" — a flood of Afro-Caribbean migrants who arrived by ship from Commonwealth countries to fill labour shortages in England after the end of the Second World War — had been improperly deported under Britain's tough new immigration regime.
Initiated by Prime Minister Theresa May in her own stint as home secretary, the "hostile environment" policy obliges landlords, employers and health workers to check the immigration status of clients and employees, essentially creating a new informal network of immigration officers.
Even victims of crime face deportation if their affairs are not in order.
"I hate to say it, but I don't think I'd have this problem [if] I had come from Canada instead of coming from Jamaica," said Anthony Bryan, a Jamaican-born Briton who was wrongly detained and threatened with removal, when he appeared before the Parliament's joint human rights committee this week.
"It was because of the colour of your skin," added Mr Bryan's wife, Janet McKay Williams, who also was threatened with deportation.
For all the diversity of its teeming capital, Britain is still incredibly clumsy when it comes to talking about race.
According to Nels Abbey, author of a soon-to-be-published book called Think Like A White Man, the immigration debate becomes a proxy for race, and commentators will "swear to high heaven that when they're talking about immigration they're not talking about race, when clearly they are … (they) are never talking about white people from Australia".
"If you accept that the immigration debate is a racial debate, then Britain talks about race more than anything else," he told the Washington Post in comments published this week.
"If you don't accept that, then Britain doesn't talk about race at all."
Media reaction to 'mixed marriage'
Meghan Markle was born in 1981 to a black mother and a white father. They married in 1979, just ten years after the US Supreme Court, in the case of Loving v Virginia, decreed that it was legal for mixed-race couples to marry.
Up until that point, intermarriage was still prohibited in 16 American states.
The surge in "mixed" marriages in the years after the court decision included, in California, the marriage of Thomas Markle to Doria Ragland (whose family line traces back to the slave workforce on the cotton plantations of the American South), and their daughter Meghan was born two years later.
In Britain, media coverage of the betrothal of Ms Markle to the then-fifth in line to the British throne was a clanger-strewn affair.
"Now, That's Upwardly Mobile!" chortled the Daily Mail, pointing out that Ms Markle's family had gone from slavery to royalty in 150 years.
The Spectator columnist Melanie McDonagh opined that "seventy years ago, Meghan Markle would have been the kind of woman the Prince would have had for a mistress, not a wife".
Daily Mail columnist Rachel Johnson, whose brother, Boris, is Britain's Foreign Secretary, wrote approvingly that "the Windsors will thicken their watery, thin blue blood and Spencer pale skin and ginger hair with some rich and exotic DNA".
"Miss Markle's mother is a dreadlocked African-American lady from the wrong side of the tracks who lives in LA, and even the sourest spinster has to admit that the 35-year-old actress is extremely easy on the eye," she went on.
Such howlers were keenly noted in the United States, where consciousness of the language around race is much sharper.
And the coverage drew an extraordinary direct rebuke from Kensington Palace, which in a statement deplored "the racial undertones of comment pieces… and the outright sexism and racism of social media trolls and web article comments" — surely the first time the British Royal family has had cause to complain about racism.
The family has also been obliged to keep a weather eye on its own ranks; the historically gaffe-prone Princess Michael of Kent apologised to Ms Markle last year after she wore a "Blackamoor" brooch to the Queen's Christmas lunch at which she met her new American relative for the first time.
Royal wedding 'a big statement'
Ms Markle's arrival is being greeted in some quarters as a powerful development in Britain.
"I struggled growing up with the feeling that the monarchy were fundamental to Britishness, but that the Britishness they represented was one that excluded me," wrote Afua Hirsch, author of Brit(ish): On Race, Identity and Belonging, in The Guardian.
"This exclusion mattered. It made other people perceive being truly British, and being black, as incompatible identities. It represented a giant taboo. Every government that I can remember made some attempt, rhetorical at least, to acknowledge and protect racial diversity. The family at the apex of our society was doing anything but.
"In recent years, the question of what it means to be British has been weaponised and politicised in new ways. Markle is, on one side of her family, directly descended from the plantation slavery of America's Deep South — a history with which all of Britain's powerful families, including the Royals, are inextricably linked. He may not have realised it at the time, but by condemning the press reaction to his relationships with Markle, Prince Harry was aligning himself with those still dealing with the fallout of that history, and its very real legacy today."
Joanna Abeyie, diversity activist and founder of the recruitment consultancy Hyden, does not claim that the wedding changes anything fundamental about Britain but argues that Ms Markle's visibility is useful.
"For Londoners and other cities in the UK, it's multicultural. So seeing mixed race relationships — I'm from a mixed-race relationship — is not entirely strange, but I think there are still parts of the UK where representation of minorities are still very underrepresented," she told 7.30.
"So I think for them this is a really big statement — to say that love sees no boundaries and actually we are going to allow someone in the Royal family to marry whoever it is they happen to fall in love with.
"I think that is a big deal and that is a big statement."