Driving with prescribed medical cannabis involves more than just holding a...

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

Driving with prescribed medical cannabis involves more than just holding a prescription. While a medical defence exists for the 2µg/L THC limit, it isn't a free pass. Drivers must notify the DVLA and remain fully fit to operate their vehicle