Despite years of therapy, the 53-year-old woman and her child - assaulted in the early hours of Boxing Day as they slept in a north London ground- floor flat - would not escape their "intense violation", according to Professor Joan Freeman, of Middlesex University.
"This will never leave them for the rest of their lives. They will never get over it. I don't think you can ever be as you were before. You have changed and it will always be there. It's not a bad cold you get over. It becomes a part of you, an experience as traumatic as this," the professor added.
Professor Freeman said the mother - who, with her daughter, was staying with a relative in Northolt for Christmas - would probably be more traumatised than the young girl.
"I think the girl stands a better chance because she's only nine and, without being dismissive, children are remarkably resilient.
"But for the mother, because she was in a position of responsibility, it will be worse for her. She's got to deal with the violation of herself and of her daughter and all that guilt."
Professor Freeman, who said the couple would need at least a year to come to terms with their ordeal and might need psychotherapy every day, added: "The mother will also have a lot of guilt to deal with. She will be guilty for herself and guilty for the child."
She added that the nine-year-old's success in coming to terms with the ordeal depended on her level of security before the assault. "How well she will get over it depends on where she started from."
Police are looking for a man said to be in his early 20s, between 5ft 11ins and 6ft tall, very thin, with thin fingers, clean-shaven and with chiselled features.Reuse content