Medical cannabis prescriptions aren't a road pass. You’re still bound by the...

https://ace-wiki.win/index.php/Is_the_UK_Basically_Zero_Tolerance_for_THC_When_Driving%3F

Medical cannabis prescriptions aren't a road pass. You’re still bound by the 2mcg/L THC limit and DVLA fitness standards. A medical defence is no substitute for your duty to drive safely