For EV drivers using medical cannabis, a prescription offers a medical defence...

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

For EV drivers using medical cannabis, a prescription offers a medical defence but doesn't override the 2mcg/L THC limit. You must notify the DVLA of your fitness to drive. Remember: legality doesn’t replace responsibility—stay safe on the road.