I saw that, too. If it's not a typo, just how old are these 'girls,' anyway?
Every year at this time, the Public Records Office releases papers which were classified for a certain period at the time, so yesterday various government papers were released from 1976 which had been held for a thirty year period, of which this was one of them.
This isn't at all obvious from the online article linked. Most of the broadsheet papers however had double page spreads on various stories from the papers released, so in the print version of the Telegraph it would be a lot more obvious that all of the sub stories were related to the archive papers, hence the fact that they don't really make it clear in the article.