Prescribed cannabis is legal, but road safety rules still apply. You must stay...

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

Prescribed cannabis is legal, but road safety rules still apply. You must stay under the 2mcg/L THC limit and meet DVLA fitness standards. A medical defence exists, but it’s not a safety net