Since the law changed in 2018, medical cannabis has been a legal treatment...

https://bizzmarkblog.com/is-medical-cannabis-used-for-arthritis-related-pain-in-the-uk-a-realistic-look-at-the-landscape/

Since the law changed in 2018, medical cannabis has been a legal treatment option in the UK when prescribed by a specialist. However, accessing it through the NHS remains rare and often difficult for most patients