Medical cannabis doesn't grant immunity on the road. You remain subject to the...

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

Medical cannabis doesn't grant immunity on the road. You remain subject to the 2mcg/L THC limit and DVLA fitness standards. While a medical defence exists, legality doesn’t replace responsibility. Being legal isn't the same as being unimpaired.