[Heyer] was first made aware of the possibility of plagiarism in May 1950, when a fan wrote to inform her of an author who had been "immersing herself in some of your books and making good use of them." She was referring to Barbara Cartland who had recently published her first three historical novels...Barbara Cartland was a socialite with connections in the "best circles," an occasional columnist for the Daily Express and the author of several works of nonfiction, three plays, and some thirty moderately successful modern romances. She had written A Hazard of Hearts [the first of a trilogy of Georgian historical novels] after a woman's magazine had commissioned her to write her first historical romance...[A]n initial cursory reading of Cartland's first two historical novels left her inclined to dismiss the author as no more than "a petty thief" of names, characters, and plot points. Among Cartland's more obvious "borrowings" were several names from Friday's Child, including Sir Montagu Revesby, alter to "Sir Montagu Reversby;" Hero Wantage, now "Harriet Wantage;" Viscount Sheringham was "Viscount Sherringham," while Lord Wrotham remained "Lord Wrotham." Georgette identified many additional "lifts" from this and others of her novels, including The Corinthian, The Reluctant Widow, and The Foundling...Aware that there "was no copyright in names" or in Regency parlance, Georgette's initial thought was to write a strong letter of protest to Barbara Cartland. but on reading Knave of Hearts, she changed her mind and wrote to her solicitor instead..."For her main theme Miss Cartland has gone solely to THESE OLD SHADES, but for various minor situations and other characters she has drawn upon four of my other novels...Georgette not only sent a cross-indexed copy of The Knave of Hearts in which she had "ringed all names and period phrase, in red ink, and indicated in black ink, giving title of my own book and page of passage, all situations identical or too like mine, and all paraphrases," but also a ten-page list of the main points of similarity between the novels, with examples of Cartland's historical and linguistic errors. It was not only Regency dialogue which her imitator appeared not to understand but also Regency fashion,,,But even worse to Georgette's mind was Barbara Cartland's "travesty" of the characters which "she had done her best to model on mine" and "a certain salacity which I find revolting, no sense of period, not a vestige of wit, and no ability to make a character 'live.'"..."I think I could have born it better had Miss Cartland not been so common-minded, so salacious and so illiterate. I think ill enough of the Shades, but, good God!, that nineteen-year old work has more style, more of what it takes, than this offal which she has written at the age of 46!"...There is no record of a response to her solicitor's letter to Barbara Cartland but Georgette later noted that "the horrible copies of my books ceased abruptly."
----Georgette Heyer by Jennifer Kloester (Sourcebooks, 2013)
And in a footnote, Kloester has this to add: "In 1971, Knave of Hearts was reissued under a new title, The Innocent Heiress, with a heading: "In the Tradition of Georgette Heyer."