Prescribed medical cannabis doesn’t exempt you from the 2µg/L THC roadside...

https://www.4shared.com/office/4hExEGiDku/pdf-94952-99400.html

Prescribed medical cannabis doesn’t exempt you from the 2µg/L THC roadside limit. A statutory defence exists, but it won’t protect you if impaired. You must meet DVLA fitness-to-drive standards—a prescription isn't a safety substitute