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

https://tiny-wiki.win/index.php/Can_I_travel_within_the_UK_with_prescribed_cannabis%3F

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 legally prescribe cannabis-based medicines like Sativex and Epidyolex