Patricia Highsmith was an accretion of oddities — a woman who doted on her pet snails and carried a selection of them in her handbag, who abandoned her native America for a restless life in Europe, and who turned a habitual paranoia into literature.

Now, 20 years after her death, her reputation has been substantially increased by film versions of her Ripley novels and, most recently, Carol (an adaptation of The Price of Salt, her extraordinarily bold novel of a lesbian love affair).