LONDON — It was an electrifying and unexpected moment in the midst of what had been a (mostly) by-the-book British wedding service. And as it went on, you could practically feel centuries of tradition begin to peel away.

Here was a relaxed, charismatic African-American bishop — Michael Bruce Curry, the head of the Episcopal Church — speaking to British aristocrats and members of the royal family in the cadence of the black American church.

But what was striking was not just his message, of love and inclusion; or his tone, which was soaring and magisterial; or his obvious delight in the matter at hand. It was the sheer fact of his prominence in a service that featured a fair number of ecclesiastical heavyweights, including the archbishop of Canterbury (who tweeted his admiration of the bishop).

The service, carefully put together by Meghan Markle and Prince Harry, included all the usual traditional elements, like a reading from the Bible by Harry’s aunt, the sister of Diana, the Princess of Wales.

It also featured a gorgeous rendition of Ben E. King’s “Stand by Me,” performed by the Kingdom Choir — a Christian group made up of black Britons that is based in southeast London and specializes in gospel music — and its leader, the renowned gospel singer Karen Gibson.

And it included prayers led by His Eminence Archbishop Angaelos, the Coptic Orthodox archbishop of London; and Rose Hudson-Wilkin, a black Church of England priest who serves as chaplain to the queen and is the speaker’s chaplain in the House of Commons.

And there was a 19-year-old cello soloist, Sheku Kanneh-Mason, the first black musician to win the BBC’s Young Musician Award in its 38-year history.

Ms. Markle’s mother is African-American and her father is white, and it is clear the bride wanted to make a point of her racial identity, to put her heritage front and center in full view of a vast built-in audience, at home and abroad. And it is equally clear that Prince Harry knew exactly what this would mean to the tradition-bound royal family.

In a place that is so white, in an institution that is so white, in a country with serious race problems, it was a gesture of profound significance. And it was a hugely symbolic moment on a global stage, with the potential to change the world’s view of the royal family, and perhaps even Britain’s view of itself.

It seems fair to say that never have so many minorities, among the congregation as well as the clergy and musicians, been in St. George’s Chapel at one time before.

It was hard to tell, looking out over the church crowd, what the general reaction was to Bishop Curry’s address. Some people looked a little bemused; a couple of royals looked as if they were on the verge of giggling, at least according to the The Daily Mail, which likes to stir up trouble, in this case with mild insinuation.

The bishop himself seemed to sense he was speaking longer than perhaps some in the crowd were accustomed to, although he was not particularly fussed about it. At one point, he appeared to hurry himself along, telling the couple teasingly: “We gotta get y’all married.” (Not everyone knew how to cope with that American expression; the BBC rendered it “you all” in its transcript.)

But outside the ancient walls of the chapel and across the country, the response was jubilant. It was as if Bishop Curry had opened the windows and let a breath of air into a room that had felt a little stifling.

People in Britain do not usually speak of love in the way he did in church. People here do not usually express themselves so forthrightly.

“The preacher is doing 50 in a 30 zone and it’s brilliant,” the BBC presenter Jeremy Vine wrote on Twitter.

Also on Twitter, a woman named Andrea L. Pinto wrote: “Rev. Michael Curry is talking about slaves finding love in the South in the face of the Queen of England. This moment is hundreds of years in the making.”

In another Twitter post, from North Carolina, Chris Burris said: “Bishop Michael Curry is quoting Dr. Martin Luther King Jr. at Windsor Castle. It’s truly a day of wonders.”

It was indeed an amazing thing to hear Dr. King’s words spoken on an occasion like this. They felt appropriate to the moment — this was, after all, a wedding — but had a larger significance, about the world in general and how we should conduct ourselves.

“We must discover the power of love, the redemptive power of love,” Bishop Curry said, quoting Dr. King. “And when we do that, we will make of this old world, a new world.”