Medical cannabis users must stay alert. While a medical defence exists for the...

https://bizzmarkblog.com/the-motorists-guide-to-medical-cannabis-dvla-rules-section-5a-and-staying-legal/

Medical cannabis users must stay alert. While a medical defence exists for the 2mcg/L THC limit, you must notify the DVLA of your status. Being legal doesn't bypass fitness-to-drive rules