In 2018, UK cannabis law changed through the Misuse of Drugs Regulations 2001,...

https://spark-wiki.win/index.php/Licensed_vs_Lawful_to_Prescribe:_What_Is_the_Difference_in_UK_Cannabis_Medicines%3F

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