Medical cannabis users must manage more than just the 2mcg/L THC limit. A...

https://oscar-wiki.win/index.php/If_I_Get_Pulled_Over,_What_Do_I_Say_About_My_Prescription%3F_A_Guide_for_Medical_Cannabis_Patients

Medical cannabis users must manage more than just the 2mcg/L THC limit. A prescription offers a statutory defence, but it doesn’t override DVLA fitness-to-drive rules. Legality isn't a safety blanket; you remain responsible for your driving impairment.