In 2011, BT was ordered to block access to Newzbin2, a Usenet archive. “It’s the first time BT has been ordered to use its Cleanfeed porn-blocking system to block non-pornographic content,” I wrote at the time. “It won’t be the last… [this] turns ISPs into censors, and of course copyright infringement isn’t the only kind of content people would like to block. We’ve had calls to ban sites that espouse extreme political views, sites that promote anorexia, sites that discuss ways to commit suicide. If BT can block Usenet archives, why can’t it block everything that anybody thinks is unpleasant or undesirable – like WikiLeaks, or anti-Scientology sites, or anything that isn’t appropriate for under-fives?”

Inevitably, more blocks followed. The Pirate Bay is (in)effectively banned by UK ISPs. There are blocks on 1337x, Abmp3, BeeMP3, BitSnoop, Bomb-Mp3, eMp3World, ExtraTorrent, FileCrop, FilesTube, Monova, Mp3Juices, Mp3lemon, Mp3Raid, Mp3skull, NewAlbumReleases, Rapidlibrary, TorrentCrazy, TorrentDownloads, TorrentHound, Torrentreactor, and Torrentz, and many more.

And now, we’re going to start blocking things that the government thinks are unpleasant or undesirable. Today, The Guardian reports that “the government is to order broadband companies to block extremist websites” and identify content “deemed too dangerous for online publication.”

The proposed blocking will follow the same model as the blocking of illegal pornography – a model whose aims are obviously laudable but whose processes have attracted criticism over false positives (where legal content is wrongly identified and blocked) and secrecy. In effect, we’ll have a secret, unaccountable organisation looking at the internet and silently blocking “extremist” content.

What does “extremist” mean? Well, it means pretty much anything you want it to mean. Over the years, our governments’ definitions of extremist have included climate change protesters, the Campaign for Nuclear Disarmament, the anti-apartheid movement, animal rights activists, environmental activists and the Occupy movement. The word terrorism appears equally flexible, so for example it can be a synonym for journalism and used to detain the partners of journalists who embarrass the government, and it can be used to arrest students too.

I know it’s cliched to talk about slippery slopes, but when you can feel the ice underneath you and you’re shooting downwards, the phrase seems pretty accurate.