Prescribed medical cannabis doesn’t grant a free pass on the road. While a...

https://magic-wiki.win/index.php/Driving,_Cannabis,_and_the_Law:_A_Practical_Guide_for_Patients

Prescribed medical cannabis doesn’t grant a free pass on the road. While a medical defence exists for the 2mcg/L THC limit, you must remain fit to drive and disclose relevant conditions to the DVLA. Remember: a legal prescription is not a safety waiver