Medical cannabis has been legal in the UK since 2018 for specific conditions...

https://angelowlnv711.yousher.com/can-i-travel-to-races-in-the-uk-with-prescribed-medical-cannabis

Medical cannabis has been legal in the UK since 2018 for specific conditions where other treatments haven’t provided relief. For runners exploring this path, access is provided through specialist private clinics following a clinical assessment