The sounds that reach Beeban Kidron's north London office are, in their way, a kind of argument. Children's voices float in through the open windows — a school on one side, a nursery on the other — and each shriek of playground laughter sits in quiet, pointed contrast to the darker material she has spent more than a decade collecting. Kidron, once best known for directing Hugh Grant and Renée Zellweger in Bridget Jones: The Edge of Reason, is now a crossbench peer in the House of Lords and the founder of the children's online safety charity 5Rights Foundation. Her new book, Users, is an account of her long campaign against an industry she believes has been allowed to damage childhoods with near-total impunity.

For most of the conversation she holds her composure with the practised steadiness of someone who has sat in Silicon Valley boardrooms and testified in parliamentary committees, but there is one memory that still breaks through. She describes watching a girl realise, in real time, that the person she had believed to be her friend was not; that the intimate acts she had performed had not been private; that strangers may have been watching. "It was her spirit, it was her trust, it was her sense of who she was," Kidron says. "It was all those things that you need to be a human being, smashed.

" The sentence lands with the weight of someone who chose every word carefully and regrets needing to say them at all. Users is not, however, a book that reads as a single sustained howl of grief.