About 2.5 million viewers tuned in Monday night to see Natalie Dormer's television movie The Scandalous Lady W on the BBC.
Digital Spy reported the ratings Tuesday.
The 18th century-set drama chronicles the real life of Seymour, Lady Worsley, "who dared to leave her husband and elope with his best friend, Captain George Bisset," a BBC synopsis said.
"Dormer plays the passionate, courageous Seymour, Lady Worsley, who escapes her troubled marriage only to find herself at the center of a very public trial brought by her powerful husband Sir Richard Worsley, played by Shaun Evans, who seeks compensation from her lover for the affair."
Co-starring Aneurin Barnard, the telepicture was penned by David Eldridge and based on Hallie Rubenhold's book, Lady Worsley's Whim, which was inspired by the full-length oil painting of Lady Worsley that hangs in Harewood House in Yorkshire.
Dormer is known for her roles in the TV shows Game of Thrones and Elementary, as well as in The Hunger Games film franchise.