Actually I think they started with th Pirate Bay and then pornography.

A quick google search: http://www.makeuseof.com/tag/5-ways-bypass-uk-pirate-bay-blo...

(screenshot of the blocking page)

I believe protection against pornography has to do with education, it's more the problem of the parents than the problem of the government. "Childs" will always find a way to view some adult content, they just need to be educated about it