Nelson's affectionate nature was most strikingly shown in his famous affair with Emma Hamilton and, as a result, she has always been a central figure in his story. Even during his lifetime, their defiantly public affirmation of their friendship attracted much attention in the gossip columns of the newspapers, and in the correspondence of those who met them. During the nineteenth century, historians argued over whether they had been lovers and then, when there could no longer be any doubt about the matter, tended to portray Emma as a scheming adventuress who led the naïve hero astray. In the twentieth century, when there was a greater acceptance of their adultery, their love affair was transformed into one of history's great romances – especially by filmmakers.

In fact their relationship was often very unromantic. The lovers were hardly ever alone – for most of their time together they lived with Emma's husband, Sir William Hamilton, in an unusual, but clearly amicable, ménage à trois. It was also a very destructive affair – closer to a Shakespearean tragedy than a Mills and Boon bodice-ripper. All the participants became figures of fun, lampooned, often cruelly, in newspaper reports and caricatures. In 1800, Sir William and Nelson were both recalled home from the Mediterranean, effectively in disgrace, at least in part because of the scandal. Frances Nelson suffered the pain of being abandoned not only by her husband but also by most of his family and friends. And Emma herself lost her hard-won reputation for respectability and never achieved the position in British society, which, as the beautiful and talented wife of the former envoy to Naples, she might have enjoyed if Nelson had not entered her life. As a result, her last years were unhappy, even tragic, with a slow descent into debt, drunkenness and death.

We know so much about the minutiae of Emma's and Nelson's relationship because so many of his letters to her have survived. He destroyed almost all of hers but she lovingly kept every one of his and, eventually, most of them were published. The original letters are now widely scattered in public and private collections, all over the world.