In the same episode of Dr Who with the wonderful hymn was some dialogue that was more in line with the modern BBC (and the oh so cool Dr Who):
Two elderly women were referred to as sisters. They demurred, explaining that they were married. Dr W seeking to normalise an arrangement that pretends to be marriage when it cannot meet its base rationale: orderly procreation and protection of children. Of course, the end result will find fake marriage reversing up the hill to claim the 'right' to have (someone else's) children, tipping its original protectiveness on its head as children become the traded badges of adult privilege.