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

https://griffinucyk847.iamarrows.com/why-does-the-uk-keep-cannabis-as-class-b

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