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

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

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.