The book and film share several similarities with the notorious murder of James Bulger at the hands of two ten-year-old boys in 1993. Jonathan Trigell has said that the character of Jack/Eric is actually based on a childhood friend of his who had struggled with life outside prison after serving a lengthy sentence (although not, as the writer states, for murder). Trigell has however admitted that the media frenzy surrounding the Bulger murderer's release at the time the novel was written did serve as an influence of sorts on the book.