Navigating medical cannabis while driving is a minefield. While a medical...

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

Navigating medical cannabis while driving is a minefield. While a medical defence exists, the 2mcg/L THC limit is strict. You must notify the DVLA of your fitness. Remember: a prescription doesn't waive road responsibility. Legality isn't impairment.