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.”