This is an opt-in feature that implements content restrictions (for e.g. parental control).
It's darkly funny that the UK is so far gone these days that people literally do not believe it.
And this is just DNS I assumed unless also keep a record of which ip addresses they actually resolve to.
To be clear I’m interested from the technology perspective and not advocating our UK friends evade government pr0n censors as a form of political protest…