Being loved by a great writer usually turns out to be less flattering to a woman than it may have seemed at first since, in the long run, we're only interested in her because he was. Up against genius, her point of view hardly stands a chance. Nor can she settle for anonymity: her association with celebrity keeps her involuntarily on show, although we can't hear what she says. Even the silence she may elect will be misinterpreted.

One such woman who could either not speak out, or chose not to, was Ellen Ternan, who was (let us say) close to Dickens for the last 13 years of his life. It wasn't her fault that the novelist fell in love with her when she was 18 and he was 45, and it isn't her fault that the attention she has attracted since her existence could no longer be hushed up as has been due to his extraordinary qualities rather than hers, whatever they may have been. She isn't to blame for the fact that the protocols of Victorian society and Dickens's unique status within it put her in an almost impossible position, both before and after his death. Claire Tomalin's excellent biography not only shows an imaginative sympathy with her anomalous situation but also wants to do her whatever justice can be done at this distance, as a person in her own right. Ellen – or Nelly as she was always known – is in a true sense this book's heroine.

The circumstances surrounding Nelly's first meeting with Dickens are well known. Dickens had got up some performances of Wilkie Collins's melodrama The Frozen Deep. Invited to present it in the intimidating space of Manchester's Free Trade Hall, he decided to ask real actresses to take over the parts taken by his daughters and friends; for male amateurs and female professionals to act together was not uncommon. An offer was made to Mrs Ternan and her daughters, and there can't have seemed any reason to turn it down. Dickens was intensely well disposed towards the theatre and was generally agreed to be overwhelmingly powerful in the main Sydney Cartonish part; he made Nelly's sister, Maria, weep on stage. Nelly herself had a minor role in the play, but a major one in Dickens's life thereafter.