I think people would lose their fucking minds. Especially the people who actually care about the monarchy, who are probably the least likely to accept this. People might not start a lynch mob and storm the palace, but at the idea that they'll have a black king in the future, the headlines aren't going to all talk in lockstep about what a "pleasant shade of coffee as well" the royals will be. And the people on the street will be saying worse.
EDIT: Saying that England is all about classism and not racism is an easy dodge, because of course the entrenched upper class is almost entirely lily white, and minorities are to a large extent shut out of moving up (to the extent there's any class mobility even among whites).
As I'm the person being backseat-sniped at and accused of an 'easy dodge' because I used an understanding of British history and society beyond that which you seem to be aware of, allow me to respond.
You are, unfortunately, looking at this backwards. You're assuming that, like in your country, the biggest social barriers and prejudices stem from racial differences, and that Britain's famously rigid social class structure itself draws its dividing lines and logic from that. It doesn't. I could point you to the stories of Indian maharajahs being treated like the kings they were in the presence of British royalty, while their servants were treated with no greater or smaller disdain than that doled out to their white counterparts. I could tell you the story of the future Edward VII dining with the future Kaiser Wilhelm II and defending the presence of the King of Hawaii at their table - 'Either the brute's a nigger, or he's a King. If he's not the latter, then what's he doing here?', he said. Yes, he called him a nigger. Yes, a brute, too. And all the paternalistic, vile racism that stems from that is rightfully to be pointed out. But, to the Prince of Wales in the 1880s, a king was a king was a king. Class trumps race every time when it comes to the upper echelons in Britain. If you want to see black people of culture and learning being screamed at for the colour of their skin, you'd need to put an old Etonian black man in a council estate in Barking. This isn't to say that Earl Henry Bufton-Tufton is going to invite him grouse shooting either, but your image of mass public disturbances is comical in how wrong it is. I also like the idea of a national newspaper ever going to print again after printing a racist headline about a member of the family of the head of state. Perhaps in America (I recall a lot of 'Michelle is a chimp' jokes), but not here.
But those are anecdotal, specific examples that make for good reading in a narrative history of the Empire but perhaps would simply get your hackles up as you'd rather impose your country's social filters on the rest of the world for simplicity's sake. It's probably better that I explain you what the actual situation would be if a black woman had emerged as William's prospective bride. The answer lies in class, no matter how hard you scream.
You hypothesise that racism exists in Britain. Of course it does. It's more widespread than we'd like to think, and it's certainly not confined to buffoons at the top of society (paradoxically, they seem to be more likely to be completely uninterested in race than they are to be actively racist) or BNP-voting dregs at the bottom. But how our hypothetical black future queen is received depends very much on her background, not the colour of her skin.
If she is of a naturalised British descent, ie born to immigrants or second generation immigrants, it's likely she is Afro-Caribbean. These seem to be the least controversial of black people in the eyes of the British public, when you look at our popular actors, television personalities, politicians and other such public figures. This is largely a matter relating to time - of Britain's black community, the Windrush generation and those who followed have been here the longest (about 60 or so years) and as such, are the most 'got used to'. Any problem which emerged here would stem from her background and decorum - but, frankly, it's ASB for William to fall head over heels in love with someone who'd be called white trash if they were white, if only for the fact he lives in a controlled environment and would never meet her. He attended St Andrews - hardly a university known for its ethnic blend (not that many are - black students in particular are notoriously under-represented at British universities, for a complex array of reasons that does not, despite assumptions, prominently feature racism) and the qualifications required to attend that institution mean any Afro-Caribbean student he had a romance with would be educated, enlightened and 'proper', and there'd be very few people who would 'lose their fucking minds' over that, as you so eloquently put it. But we're getting off track.
If she were African, and, say, spoke with a thick Nigerian accent, then we're getting into territory where some Britons would feel more comfortable openly voicing some questions about suitability. They'd still be being racist, of course, but this is a matter again derived from the more recent African immigrant populations, and their perceived harshness (there is a stereotype of an angry, aggressive and unhelpful black African nurse present in NHS institutions, one that I can say from experience did not emerge from thin air). But even then these people would be a minority that outraged and embarrassed the majority, provided she is again suitable, but once again she wouldn't get to the stage where she'd be revealed to the public as a fiance if she were not. A cultured, intellectual and kind Ghanaian being mother to a future sovereign is going to upset some mouthbreathing knuckledraggers in the valleys but by and large she's not going to inspire a lynch mob.
I hope this has made clear why your comments have inflamed such a degree of zealous correction from myself and my fellow Britons. Othyrsyde's points are broadly fairer, but misses the mark when he/she says 'bringing up the fact that most of the upper class in UK is white is a valid point in discussing race vs. class'. Er, the
entirety of the upper class in the UK is white. But that doesn't make it a valid point (or, indeed, a point at all) in a discussion of racial factors or social factors being the biggest stumbling block in British society. The upper class's entrenchment and unassailable position at the top of the social ladder (but not the real-world ladder - our country, businesses and governmental systems are run by the upper-middle class, which slowly but surely is becoming more ethnically diverse by the very nature of immigrant generation integration) is a phenomenon that dates back more than a thousand years before the Windrush came back from the West Indies. If you're not born into it, you're not getting into it. Because none of those Norman knights, Hanoverian nobles, or adjutants to Wellington, Nelson or Henry V were black, a black presence in the upper class isn't going to happen in this country, any more than there'll be a presence of trade unionists or public sector workers. It's not racism, it's classism - and it's not even active anymore. It's been passive for centuries.
Having read and reread your edit, in response to my comments above about Othyrsyde's version of what you said, I'm still trying to fathom what exact point you're trying to make. There are no black people in the upper classes because of long-term social reasons that you accept, therefore the upper classes are all racist and would shout and scream about a black princess? You may need to clarify what you mean, because at the moment all I'm seeing here is an Anglophobic non-sequitur.
I agree that if you want a greater controversy, you have to go for someone of Asian (actual Asian, not what the Americans call Asian) descent. Islamic faith would also cause a stir. Or, heaven forfend, Catholicism...
This is bizarre. I typed exactly as much as I felt I needed to to make my argument, and I'm going to continue to do so. If I wanted to end the discussion, I'd do it, and now I am. I'm done with this.
On a note of truce (and as someone who has just, as you did, typed out what I felt was necessary to make my points), I would like to echo how ridiculous Turquoise Blue's warning seemed. What she was referring to was 'textwalling', which I believe has indeed led to kicks in the past but in those cases we were talking about pages and pages and pages of text that no-one would ever possibly have the time or energy to respond to. Not 'a medium sized post', as yours was. I'd say yours wasn't even that long - this one's long!
