Legally prescribed cannabis is a reality, but road safety rules remain firm....

https://www.novabookmarks.win/medical-cannabis-is-legal-but-uk-drivers-face-a-strict-2-g-l-thc-limit-a

Legally prescribed cannabis is a reality, but road safety rules remain firm. Even with a valid medical defence, you must stay under the 2µg/L THC limit and satisfy DVLA fitness-to-drive requirements