Prescribed cannabis is legal, but the 2µg/L THC limit applies to all. A medical...

https://www.social-bookmarkings.win/prescribed-cannabis-isn-t-a-free-pass-while-a-medical-defence-exists

Prescribed cannabis is legal, but the 2µg/L THC limit applies to all. A medical defence needs you to be unimpaired. You must tell the DVLA of your fitness. Legality isn't immunity; you remain responsible for safety