Medical cannabis is legal, but UK drivers face a strict 2µg/L THC limit. A...

https://bizzmarkblog.com/the-motorists-guide-to-medical-cannabis-dvla-rules-section-5a-and-staying-legal/

Medical cannabis is legal, but UK drivers face a strict 2µg/L THC limit. A medical defence exists, provided you’ve notified the DVLA. Crucially, legality isn’t roadworthiness