They also take many forms. The exhibition ranges from early 20th-century classified ads seeking same-sex romance to sweethearts' letters to soldiers at war and a medieval song about heartbreak.
There's also "one of our most iconic documents," Iglikowski-Broad said, referring to a poignant letter to Queen Elizabeth I from her suitor Robert Dudley, Earl of Leicester.
Written days before Dudley's death in 1588, it conveys the intimacy between the "Virgin Queen," who never married, and the man who called himself "your poor old servant."
The missive, with "his last lettar" written on the outside - spelling at the time was idiosyncratic - was found at the queen's bedside when she died almost 15 years later.
Love, in the exhibition, doesn't just mean romance. Family bonds are in evidence in Jane Austen's handwritten will from 1817 leaving almost everything to her beloved sister Cassandra, and in a 1956 letter in which the father of London gangster twins Reggie and Ronnie Kray, implores a court to go easy on the brothers, because "all their concern in life is to do good to everybody."