Unpublished correspondence from 1950 reveals Heyer's outrage at discovering from a fan the similarities between, among others, Cartland's Knave of Hearts – the third part of a Georgian trilogy – and her own These Old Shades, a Georgian romance novel.
She continued: "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".
But Heyer herself would put her work down, writing to her publishers in 1943 of Friday's Child that "judging from the letters I've received from obviously feeble-minded persons who do so wish I would write another These Old Shades, it ought to sell like hot cakes".
Unlike her first novel, These Old Shades focused more on personal relationships than on adventure.
In 1926, she released These Old Shades, in which the Duke of Avon courts his own ward.
After her novel These Old Shades became popular despite its release during the General Strike, Heyer determined that publicity was not necessary for good sales.
To meet their expenses Heyer sold the Commonwealth rights for These Old Shades, Devil's Cub, and Regency Buck to her publisher, Heinemann, for £750.
In May 1950, one of her readers notified her that Barbara Cartland had written several novels in a style similar to Heyer's, reusing names, character traits and plot points and paraphrased descriptions from her books, particularly A Hazard of Hearts, which borrowed characters from Friday's Child, and The Knave of Hearts which took off These Old Shades.
Old shade trees lined the road, and wildflowers grew in the fields.
Most are set on large lots, with ample lawns and old shade trees.
She cannot forget the vanished neighbors, a racially mixed assortment of middle-class strivers, or the century-old shade trees that, one by one, succumbed to neglect.
