Prescribed medical cannabis is legal, but driving is a separate issue. Even...

https://telegra.ph/Can-I-Drive-My-EV-the-Same-Day-I-Start-Prescribed-Cannabis-The-Reality-of-Roadside-Law-04-23

Prescribed medical cannabis is legal, but driving is a separate issue. Even with a prescription, exceeding the 2µg/L THC limit can lead to prosecution. While a medical defence exists, you must first satisfy DVLA fitness-to-drive requirements