I ask again, how is blocking a few search terms on a search engine going to stop child abuse content and make children safer? Leaving aside, of course, that this content is already blocked by the BT cleanfeed system.
Let's not forget that the greatest threat to children comes from someone known to the child. The overwhelming majority of cases of child abuse involve a family member, family friend or person of authority abusing their position of trust.
Cameron is focusing on the minority threat while ignoring the majority threat (not that the threat comes from Google anyway), and that will leave children in more danger.