In 2018, UK cannabis law changed through an update to the Misuse of Drugs...

https://lanesinterestingthoughts.lumenforgex.com/posts/what-is-the-gmc-specialist-register-and-why-does-it-matter-for-cannabis

In 2018, UK cannabis law changed through an update to the Misuse of Drugs Regulations 2001, not the Misuse of Drugs Act 1971