Charles Dickens' Teen Mistress Ellen Ternan

Here's IMDb's description for The Invisible Woman (2013):

At the height of his career, Charles Dickens (Ralph Fiennes) meets a younger woman who becomes his secret lover until his death.

The British film is based on 45-year-old Charles Dickens’ thirteen year affair with 18-year-old Ellen “Nelly’ Ternan, which began in 1857 when Ellen was an actress in a play that was produced by Dickens. 

In an effort to avoid tarnishing his image and to keep their age-gap affair a secret, Dickens purchased a house for Ternan close to London. On one of his secret visits, Dickens impregnated the nymphet, and they had a son that they hid, even further away, in France.

The British film was shown at the 51st New York Film Festival. And for more information, one could reference Claire Tomalin's paperback, The Invisible Woman: The Story of Nelly Ternan and Charles Dickens.