It was more intrigue than love at first sight. When the British interior designer and antiques dealer Rose Uniacke initially visited the home where she now lives, on Warwick Square in London’s Pimlico, she was struck by its singular qualities but ultimately was content to walk away.

“It was too large, too damaged, and most definitely too big a project,” she writes in her new book, Rose Uniacke at Home, which is dedicated to her Warwick Square undertaking and will be released by Rizzoli on October 26. Years would pass between the first time she and her husband, film producer David Heyman, toured the 19th-century property—a brick Victorian, quite unusual for the area—and their ultimate decision to purchase it, in 2007.

The main hall.

Even still, Uniacke—who is as restrained in her taste as she is discreet about her famous clientele (the Beckhams, perfumer Jo Malone, The Crown creator Peter Morgan)—recalls how she was immediately impressed by the unusual nature of the building. In a neighborhood populated by quintessential white-stucco-clad terrace houses, the Pimlico House stood out like an imposing Victorian institution. It hadn’t been modernized since it was first constructed to serve as Scottish portraitist James Rannie Swinton’s home, studio, and art gallery—a combination of spaces that required meaningful square footage and an abundance of natural light.

The sprawling, historic structure survived being bombed in World War II and was then abandoned for decades.

The drawing room.

Though the property was in dire need of work, Uniacke resisted the urge to do too much. “We explored how to repair and renovate it in the appropriate way,” she says. The transformation was slow and deliberate. “That was definitely my intention—to use a bit of a light touch, to restore it so that it’s still sort of correct and more elegant than its earlier form. But then, once that’s done, you can allow yourself some poetic license to move it into the 21st century, as it were.”

To achieve this delicate aim, Uniacke collaborated with noted architect Vincent Van Duysen. “My intervention, under Rose’s attentive supervision, was based on rethinking the architectural scale and spatial character of the building while helping carve a family house out of it,” Van Duysen says of the partnership, before conceding: “Obviously, the undertaking was not without its fair share of challenges.”

It hadn’t been modernized since it was first constructed to serve as Scottish portraitist James Rannie Swinton’s home, studio, and art gallery.

The result—with its alchemical blend of light, texture, original details, and scale—is dreamy. And while Uniacke is celebrated for her work’s restraint and serenity, she does not rely on a prescriptive formula, either when taking on a commission or one of her own projects. Instead, she prefers to tap into a space’s inherent personality and emphasize elements of it.

The screening room.

“In classic architecture or contemporary architecture—whatever it is—what you want to enhance, what you want to play down, is different in every place,” says Uniacke, who this fall is opening a second London home-décor store, opposite her current showroom, devoted to textiles and a new line of environmentally sensitive paints.

One of the primary goals when restoring this particular building was to “downplay the grandeur of the space,” she says, taking a structure that felt like an untouched Venetian palazzo and reimagining it for everyday life.

Every decision along the way was in service of function, and Uniacke is still re-evaluating the spaces, tweaking small details, moving furniture around to accommodate the way light falls during certain times of the year. (That sensitivity to light and proportion is captured beautifully by François Halard in the forthcoming book.)

The kitchen.

“You know how, if you live in a space, you stop seeing it?” asks the designer. “I just want regularly to look around, so that sometimes I can make changes or things evolve—whatever it is, I am always doing it.”

Uniacke wanted to add an airiness to the main hall, so she and Van Duysen conceived a cantilevered stone staircase and added large arched doorways that echo original ones located at the back of the building. The space features a copper-floor installation by Carl Andre, a 19th-century mirror, and a reinstated fireplace, which is frequently used, imbuing the space with a welcoming warmth.

The drawing room, anchored in one corner by Uniacke’s childhood piano, is a favorite place to gather with family and friends. Deep sofas and armchairs, a Tuscan refectory table, a mix of objects—a large Warring States Chinese urn, a piece of Lalique glass—and a group of Francis Alÿs drawings create an aura of relaxed intimacy.

One of the primary goals when restoring this particular building was to “downplay the grandeur of the space.”

“It has an informality that I love,” says Uniacke of the dining room, which features a table made from an original draper’s model, surrounded by Kaare Klint chairs from 1930. Always wanting the home’s history to shine through, the designer elected to leave the columns raw. Yayoi Kusama’s Infinity Nets (2000) hangs above the dining table, lending the space “a mesmerizing quality,” notes Uniacke. “[The painting] feels uplifting, calming, unpretentious, and has the strength to hold the room.” Errol, the family dog, patiently awaits suppertime.

The dining room.

Though “not huge,” Uniacke says, the kitchen is large enough to easily move around in. To achieve that, she removed an original island in favor of a small breakfast table. The 1930s Syrie Maugham cone lights inspired a reproduction Uniacke sells in her Pimlico shop. An abstract painting by Ryan Sullivan adds “colorful energy” to the room. A walk-in refrigerator is cleverly disguised behind the jib door in the corner.

The house’s original studio now functions part-time as a screening room. (A hole was cut in the painter’s canvas hanging on the wall for the projector: “A sort of playful way to deal with it,” Uniacke says.) Not one for finality in design, she is constantly moving furniture around to suit a given function, the bookcase being the only constant. The large table is a perfect spot for projects, books, and card games. The Genoese chandelier draws the eye up, underscoring the room’s impressive height, while everything else is intentionally low-slung, “to feel comfortable and domestic.”

The pool.

“This is probably where I would be if I was alone in the house in the evenings,” Uniacke says of the study she shares with her husband. Originally the ballroom in James Rannie Swinton’s home, it’s “a sunny room, it’s very light, and the yellow curtains bring more of that sunshine feel in,” she adds. A large black-and-white self-portrait by Sarah Lucas “balances the window and frees the fireplace from having to hold the room completely.” Two ebonized chairs sit on either side of a partners desk, all Regency.

A pool was installed in the building’s basement, where the emphasis was on creating energy through the reflection of light off of water and glass. Uniacke wanted this level to feel a bit more contemporary than the upper levels, installing primarily 20th-century furniture throughout. The Orkney chairs were woven from straw in 1900 and add to the coziness of the room, where Uniacke likes to relax before or after swimming.

The winter garden.

The winter garden is arguably the home’s most striking space, especially when lit by candles in the evening, and speaks to the painstaking efforts Uniacke took to preserve the edifice’s original bones. Working alongside landscape designer Tom Stuart-Smith and Van Duysen, Uniacke removed the original Victorian glass dome and crafted a space conducive to growing many varieties of plants. (“It has been a gradual evolution,” Stuart-Smith says of their choices in plantings. “I hope they will be the sort of gardens that just get better with time.”) A late-19th-century marble fountain, which was once in the window of Uniacke’s shop, now stands in the corner and fills the room with the music of moving water.

David Foxley is the Executive Editor for Air Mail, overseeing its online shop, Air Supply

Rose Uniacke at Home comes out from Rizzoli on October 26