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. This allowed specialist doctors to prescribe cannabis-based medicines like Sativex and Epidyolex