The painting wasn’t much to look at. Dark and shadowy, it depicted a biblical scene: namely, David perched over the decapitated head of Goliath. Attributed to Italian painter Giovanni Francesco Guerrieri when it first appeared on the auction circuit in 1975, the artwork landed in the London-based studio of conservator Simon Gillespie some four decades later.

“It was one of those paintings that was easy to walk past,” Gillespie tells David Sanderson of the Times.

But careful cleaning and analysis of the painting has revealed its finer details—and produced key indications that the work was actually created by Artemisia Gentileschi, a 17th-century Baroque artist known for her dynamic paintings, which place a radical emphasis on the agency and perspective of their female subjects.

Art historian Gianni Papi initially suggested that David and Goliath was painted by Gentileschi in 1996. He based his assessment on a black-and-white photograph of the artwork, as its location was unknown at the time. Then, in 2018, the painting resurfaced at an auction in Germany. It was initially attributed to “a seventeenth-century painter of the school of Caravaggio,” according to the Simon Gillespie Studio, only to be listed as a Gentileschi the day before the sale.

The buyer—who wishes to remain anonymous, according to Joanna Moorhead of the Art Newspaper—enlisted Gillespie to analyze and treat the artwork. David and Goliath was in need of a cleaning; over the years, it had accumulated dirt, varnishes and overpaint. As experts stripped away the build-up, they uncovered signature Gentileschi details, including the sparse landscape in the background, the ochre color of David’s cloak, the rendering of his sleeve and the way light falls across his face. Then came the most stunning revelation: a faint signature spelling out the artist’s name along the hilt of David’s sword.

“Finding the signature during removal of the overpaint was an amazing moment,” says Gillespie in a statement.

Writing in the Burlington magazine, Papi suggests the painting may have originated from the collection of England’s Charles I. Gentileschi, who was born in Rome, traveled to London, where she worked for the king alongside her father, artist Orazio Gentileschi, in 1638. During the late 18th century, in fact, art historian Horace Walpole noted that “King Charles had several of [Gentileschi’s] works,” and that “her best was David with the head of Goliath.”

Historically, Gentileschi’s artworks have been largely ignored or misattributed to male painters, chief among them her father. But recent years have brought new attention to her canon and legacy, ushering in a new age of Artemisia. In November of last year, a newly discovered Gentileschi painting sold at auction for $6.1 million, smashing records for the artist. And next month, the National Gallery in London will launch a major exhibition of Gentileschi’s work—one that also sheds light on her challenging biography.

Gentileschi’s talent emerged at an early age. She studied under her father, who was friends with Caravaggio, a preeminent Italian painter who greatly influenced her art. When she was 17, Gentileschi’s father placed her under the tutelage of painter Agostino Tassi, who raped her, then refused to marry her. Orazio pressed charges against Tassi—at the time, women were barred from pressing rape charges themselves, so Orazio acted on his daughter’s behalf, detailing the decline in “bartering value” inflicted by her loss of virginity—leading to what must have been a horrifically traumatizing trial for Gentileschi. As part of the court proceedings, she was subjected to a gynecological exam and tortured to prove the veracity of her claims. “It is true,” she is said to have cried as her fingers were crushed with a thumbscrew-like device. “It is true. It is true. It is true.”

Tassi was found guilty and exiled from Rome—a sentence that was never meted out. Gentileschi subsequently moved to Florence, where she married artist Pierantonio Stiattesi and became the first woman to gain acceptance to the Accademia delle Arti del Disegno, or the Academy of Arts and Drawing. Her most famous paintings vividly imagine famed mythical and biblical women in moments of agony, vengeance and triumph—a trend that many critics see as a response to Gentileschi’s fraught personal history.

In one painting, Gentileschi renders a dramatic portrait of Lucretia, who, according to Roman tradition, was raped by a tyrannical prince. She depicts the moment before Lucretia decides to commit suicide—not defeated, but determined. In Judith Beheading Holofernes, meanwhile, Gentileschi shows the biblical woman in the midst of beheading an invading general she had seduced.

“She’s imagining, as a woman, what it would take to decapitate a muscular man,” Letizia Treves, curator of the National Gallery exhibition, tells Moorhead in a Guardian interview. “You see the determination and resolve in her face.”

David and Goliath will not be featured in the new London show; nor does it exemplify Gentileschi’s pioneering portrayals of female subjects. But as Gillespie tells the Art Newspaper, the painting does highlight its creator’s “extraordinary sense of narrative.”

“It’s a genius piece,” he adds. “This was my first time working on a painting by her, and it has opened my eyes to the character of the woman.”