In the chapel of Christ's College, Cambridge, some twenty years ago, historian Alan Bray made an astonishing discovery: a tomb shared by two men, John Finch and Thomas Baines. The monument featured eloquent imagery dedicated to their friendship: portraits of the two friends linked by a knotted cloth. And Bray would soon learn that Finch commonly described his friendship with Baines as a connubium or marriage. There was a time, as made...