If its indeed the case as stated that even 20 mg of alcohol in the blood is "severely disabling" then im very suprised the CAA allow for eg licensed aircraft engineers to have a limit of 80mg one would assume that given the fact your severly disabled with a level of 20mg you would be virtualy comotose wth 80mg and in no fit state to be near a aicraft let alone carrying out vital safety related tasks,something doesnt quite add up here