one of my in-laws is on BT Broadband/FTTC service, and has enabled the content protection service on the HomeHub.
if you try and use a third party resolver, such as Google, you web requests get redirected to a warning page saying you're not allowed to do that. so it's not a big leap to imagine BT and the other ISPs operating under Cleanfeed to simply block access to any resolvers other than their own, and either redirect DNS requests to regular resolvers or to some which specifically cause users' web traffic to get the naughty page. The net result will be that everyone will start using VPNs. I'd never downloaded music from a, ahem, alternative source, until a CD I owned legitimately wouldn't play on anything except the dumbest CD player because the copy protection broke the Red Book standard. So, start routinely breaking people's access to the internet and they'll make the effort to discover how to bypass it.
