The censorship capability that BT and later other major ISPs have been building into the UK Internet has now hit the mainstream after the blocking of a Wikipedia page. Bizarrely, BT themselves seem not to be blocking the album cover at issue, leaving that to Virgin Media, Be Unlimited/O2/Telefonica, EasyNet/UK Online, PlusNet, Demon, and Opal.
There is much more information in a book chapter of mine that should be published any day now: Internet censorship — be careful what you ask for. You can also read about the opaque way in which the so-called Cleanfeed system came about in our report on self-regulation for the European Commission.
Before the government and these ISPs march us any further down this road, they might like to think about more effective mechanisms for removing child abuse images from the Internet, rather than strangling at birth the Internet's support for freedom of expression.