Procedural?
Similar thing in Area Control. I'd like to think that I could still provide a procedural service in event of a radar failure, but in reality the skill has probably atrophied. The Regulator recognises this and London Area Control is not approved to provide a non-radar area service except as a short term expedient to clear traffic in event of radar failure....no new traffic would be allowed. Quite sensible in my view...I wouldn't like to risk lives using methods that are not regularly practiced.