Well, if you build a wall, someone is going to try and get over under or around, it's important we collaborate on such important issue.

We do take a lot of effort to remove and report this content, but we do accept that there is more work can be done. We are very happy to do that.

But immediately people are searching for evidence that will make any real difference.Halting predictive text on searches might stop the innocent been inadvertantly ,so might warnings of binding legal behavior. But experts in child protection say it won't block determined pedofiles.

This is the beginning and not the end. And it's a small step forward not a huge one when it comes to actual child protection. What we need to see now is the Prime Minster's focus and influence being used to help us catch the predators.

Google says they've had two thousand staff developing new technology to identify and block child pronography. The rival Microsoft has already developed the ability to recognize illegal photographs and track them when they are copied and distributed. Now google says they've been able to do the same with video.

The program allows analysts to break down every video to calculate a unique digital signature. That signature is then matched again other versions online even if they've been edited or altered. Once they've been identified, all copies are then deleted from the Internet.

Stewart Hazzel scoured the web for under-age pronography before murdering to a shop. But most images shared by pedofiles are downloaded somewhat closed networks beyond the capacity of Internet search engines. That requires global police action.

You can go after these pedofile sharing, you can take down a site, you can prosecute these people. And I want to see, you know, people being prosecuted for these crimes. We are putting the resources into the police, into the National Crime Agency, walking in all steps with the Americans to make sure we go after these people.

Campaigners like Sarah, whose daughter Sara was killed by a sex offender,say there is only one way to really tackle the problem.

Mr Cameron, plice, just fund police properly so they can do this and get better of this. And be a force to * ,so the pedofhiles don't * us any more.

Where borings can easily been ignored, tracking online petitors to their homes is the real challenge.