[pmyteh]

There was a law passed (Digital Economy Act 2017, pt.3[0]) but it's basically been shelved anyway as impractical.

In the UK many laws don't take effect immediately, but only on 'commencement' (normally by government order). If you look at the Archives copy of the act in the link, you'll see that there are several sections marked 'prospective' (not yet commenced). Although it looks like section 14 (the operative one which puts a duty to prevent access to under 18s) has been commenced, if you look at the footnote it only has been 'for specified purposes' and if you click through to look at the commencement order it's only actually in force for the purposes of subsection (b) (the Secretary of State may make regulations to define 'commercial basis' for pornography).

Although this is terribly confusing for people trying to work out what the laws are, it isn't unusual. It'll probably sit in this limbo state on the statute book for a good length of time and then be cleaned up by repeal next time the government passes a law in a similar area.

Or it might just sit there. The Easter Act 1928[1] setting a semi-fixed date for Easter is still extant but not in force. There may be older laws yet.

[0]: https://www.legislation.gov.uk/ukpga/2017/30/part/3

[1]: https://en.wikipedia.org/wiki/Easter_Act_1928