LONDON — The Queen Victoria Memorial, centerpiece of the plaza that fronts Buckingham Palace, is possibly the most bombastic of this city’s monuments to British grandeur.

Beside Victoria, queen and empress, glowering toward the Mall, is a cascade of allegorical statuary representing Courage and Constancy, Truth and Justice, Manufacture and Agriculture, Peace and Progress, and Motherhood. Ship’s prows jut from the corners. Bas-relief mermaids and mermen watch over its fountain pool. Dedicated in 1911, the edifice projects the historical certainty and moral satisfaction of the Britannia that ruled the waves.

Kara Walker was on her way to Heathrow Airport from her initial site visit to the Tate Modern, after being selected for the museum’s annual Turbine Hall commission, when she saw the memorial from her taxi.

“I hadn’t even seen it before,” Ms. Walker recalled recently at her Brooklyn studio. “I took a bunch of pictures out the window, because I was like — this is so totally my thing.”

Ms. Walker’s installation, the latest in the high-profile series that began in 2000 with Louise Bourgeois, opens this week in the cavernous atrium of the power plant-turned-museum on the south bank of the Thames, and runs until April.

She has built a twisted counterpart to the Victoria Memorial — a fountain whose jets emerge from the nipples and open jugular of a Venus figure 40 feet up, feeding a basin populated by sailors and sharks.

On the monument’s core and around its edges, she has installed allegorical figures of her own that offer a sardonic counterprogram to the celebration of empire. They display her hallmark style — grotesque, often violent, and layered with art-historical references and sideways cultural comment.

The original Victoria Memorial was funded in part by gifts from the dominions of Canada, Australia, and New Zealand (credited), along with proceeds (uncredited) from goods brought from West Africa.

In response, Ms. Walker presents her countermemorial, titled “Fons Americanus” — the Fountain of America — as an offering from a colonial subject: “A Gift and Talisman,” reads the text stenciled on the gallery wall, for “the Citizens of the Old World (Our Captors, Saviours, and Intimate Family),” from “That Celebrated Negress of the New World, Madame Kara E. Walker.”

In its manner and themes, the work flows coherently from Ms. Walker’s well-known genus of drawings, silhouette cutouts, films and sculptures that explore domination and resistance, particularly in the antebellum, plantation context, with unflinching attention — too much, for some viewers — to its moral and physical perversions.

It has made her, deservedly, one of the fundamental contemporary investigators of the American psyche, and of the racial anxieties that the United States has yet to purge. But her projects overflow national boundaries and respond to history that began well before the arrival of enslaved Africans in what is now the United States in 1619.

“It does drive me a little bit crazy when I see references to my work that say ‘slavery in America,’” she said. “I’m talking about power dynamics, kind of universally, and also in the New World, or in the world that was created by the imperial project.”

Ms. Walker’s first large public commission, in 2014, the spectacular “A Subtlety, or the Marvelous Sugar Baby” in the predemolition Domino factory in Brooklyn, began to make this perspective explicit. The site was where, for decades, most of the raw sugar for the East Coast market arrived from the Caribbean, the product of centuries of slavery and colonial exploitation.

Now, in London, she has made her way to the source.

“It’s a reversal of the triangle trade, going from America via Africa back to England,” she said, laughing. “Or thinking of it as a different shape — a circle, a cycle.”

Turbine Hall hosts prestige commissions — past artists include Olafur Eliasson, Ai Weiwei, and last year, Tania Bruguera — but the space is awkward. The hall is soaring, like a cathedral, with museum galleries rising in wings on either side. It is a place of passage and gathering.

“It’s parklike, in a weird way,” Ms. Walker said. “I’ve heard that babies take their first steps in there. I’ve been there when it’s empty, people sit on the floor. There’s something blank-slatey about it, for the general population, and I find that fascinating.”

Matching her ideas to the space took time, she said, with months “going down paths that felt wrong, wrong, wrong,” feeling pressure from the timeline. Seeking fresh inspiration by drawing, she found herself fixating on water, then fountains, and remembered her photos of the memorial. “And it was waiting for me,” she said.

Ms. Walker turned to designing the characters who would inhabit the “Fons Americanus” tableau. After the Sugar Baby, which was built by a team from her drawings, she wanted a more personal experience.

“It was a little too removed from my hand,” she said.

On shelves in her studio, she showed clay models she had made for her figures, along with rejects and outtakes. She had not worked with clay since she was a child, but she said the figures “just appeared” as she handled it. “As people who work with clay sometimes will tell you, the form was just in there, screaming to get out.”

With Millimetre, a fabrication company in Brighton, she found a process to preserve the handmade feel in the final pieces. Her tabletop versions were molded and coded, then fed through Powermill, a digital milling program, to a robot that reproduced the shapes from bricks of Portuguese cork. (The material was chosen for its environmental sustainability).

Artisans coated the pieces with layers of Jesmonite, a plaster and resin composite, selected to take the color of Portland stone, common in London buildings, and carefully reproduced the details of Ms. Walker’s touch by knife before it set.

The irregular finish of the statues contrasts with the smooth sheen of the central pedestal and the lip of the fountain, suggesting a story in motion, said Clara Kim, the Tate curator who worked on the project.

“Her intention was that it is a memorial that is in the process of being formed,” Ms. Kim said. “As if emerging from the ground, from the depths of history.”

Visitors unaccustomed to a Kara Walker project may find some of the specific histories in “Fons Americanus” difficult or perhaps shocking.

The parts that riff directly off the Victoria Memorial read as biting satire. One figure, “The Captain,” scowling and with legs spread, is inspired by Marcus Garvey or the fictional Emperor Jones, both ambitious liberation fighters turned autocratic. To his left is the “Kneeling Man,” a white colonist whose humble stance may conceal nefarious intentions.

There is also “Queen Vicky,” a caricatural African figure carrying a coconut, whose skirt shelters a figure Ms. Walker calls “Melancholy.” Another, “Angel,” is a tree trunk and branches, from which a thick noose dangles.

Placed about the basin, some partially submerged, are scenes that allude to artworks that treat the dread of the Middle Passage, such as Turner’s “Slave Ship,” depicting slaves thrown overboard in a storm so the captain could collect insurance money.

A researcher by instinct, Ms. Walker shares reference images in the catalog. They range from Delacroix and Matisse to the photograph of a pit, in a port in Sierra Leone, where those who refused to board the slave ship were tortured and killed. A smaller sculpture that refers to this horror greets visitors as they enter the hall: water streams from a fountain through the eyes of a severed head.

In another hard moment, Ms. Walker has sculpted a Pietà scene in which a male figure lifts a body whose mangled face clearly makes reference to the murdered Emmett Till — and with it, the 2017 controversy over “Open Casket,” the Dana Schutz painting in the Whitney Biennial. (Ms. Walker obliquely defended the work, lauding the value of even violent depictions in art as a “site of potentiality, of query.”)

“Since that erupted on the scene, I was thinking about the image,” Ms. Walker said.

“Not the image of Emmett Till himself, but the silent mourning and secret tragedy of the caregiver, the love, the parent. The retrieval, unwinding the bodies from the tree, picking up bodies out of the river or the ocean.”

She drew a connection to the deaths of migrants in the Mediterranean. “It can’t really be spoken so much,” she said. “The ocean is the thing that matters. The river, the water, it’s the entity that really knows.”

Is London ready? Ms. Kim, the curator — who is American, and previously worked at the Walker Art Center in Minneapolis and other institutions — said it should be.

“We didn’t know when we invited her that she was going to do something on monuments,” she said. “But it’s such an apropos subject given the discourses that are happening now around re-evaluating monuments, certainly in the context of the U.S. It’s important that those conversations happen here as well.”

Ms. Walker said she learned from “Sugar Baby” that everyone will have a different reaction, and that she welcomed that. “As long as it’s lively,” she said. (A show of her video pieces over the years, curated by Hilton Als, is opening this week at Sprüth Magers gallery in London.)

Making work in Britain, she said, forced her to “get over whatever the weird prejudices were” that she felt about the place, mixed with knowledge of her ancestry — a great-great-great-grandfather, Abraham Thorpe, was a white man from Derbyshire whose grandson had a black child in South Carolina.

She envisioned the work as being for the British public — caught up, like the American public, in the fraught ongoing project of building a pluralistic society.

“I think of it in terms of people,” she said of her monument. “A gift toward some democratic ideal.”

Kara Walker: Fons Americanus

Oct. 2-April 5, 2020; Tate Modern, London; tate.org.