I had no idea this was ever a thing: apparently the question of whether a man could marry his deceased wife's sister had the political moralists of Britain in knots for centuries -- including recent ones. Kind of puts the gay marriage debate into some perspective:
The drama begins in 1835 – before which year marriages with deceased wive’s sisters were not void, but voidable by legal action. Henceforth they were illegal in Great Britain. From 1841 to 1909 there were 35 failed attempts to fire through Parliament successive shafts from a whole quiver of deceased wife’s sister marriage bills. ...
From the Saturday Review, in 1876: "an example of the diseased craving for abnormal enlargements of personal liberty which is the seamy side of Liberalism."
It would take a man more than a year, reading the equivalent of a book a day, to toil through the vast morass of literature inspired by the theme of marrying a deceased wife’s sister. Among the more engaging titles are those of the earlier treatises; for instance, Charles Blount’s To HisFriend Torismond, to Justifie the Marrying of Two Sisters the One After the Other (1695), or John Quick’s A Serious Inquiry into the Weighty Case of Conscience Whether a Man May Lawfully Marry His Deceased Wife’s Sister (1703) …It was not until 1907 that this remnant of Leviticus (actually a misinterpretation of Leviticus, I think) was removed from British law.