Since 2018, medical cannabis is legal in the UK via private clinics for those...

https://mill-wiki.win/index.php/Navigating_the_Gray_Area:_How_Anti-Doping_Thresholds_Work_for_THC_in_Sport

Since 2018, medical cannabis is legal in the UK via private clinics for those with specific conditions if other treatments failed. Competitive runners: WADA strictly prohibits THC in-competition