"At the time Milly was a bit upset about it, not much for herself but her mum. I know that Milly did see them and there was more than one of them."

During the trial Bellfield's lawyers used this testimony, along with a "goodbye" note that Milly had written to her parents and a poem in which she said "I hate myself," to paint a picture of the teenager as unhappy and distressed. His tactics caused great distress to the family, but the jury failed to believe his plea of innocence.

Geoffrey Wansell, the author of a book on Bellfield, "The Bus Stop Killer," told CNN that in the wake of the 2011 trial, during which the Dowlers were pilloried by the tabloids over the pornography revelations, the family grew to loathe the press. It was in this atmosphere that the revelation was made about the hacking of Milly's phone, which became, according to Wansell, "the defining moment from which News of the World could not recover."

"I don't think it's as simple as the fact that Milly Dowler's phone was hacked and that led to the end of the News of the World. I think there are more layers to the story than that, and we may never know what actually happened."