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

https://evpowered.co.uk/feature/medical-cannabis-and-uk-driving-laws-what-ev-owners-must-know/

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