8 hours bottle-to-throttle used to be the rule. Increased to 24 hours or more for heavy drinking.
Since the recent regulations stipulating a maximum blood-alcohol level came into force, I believe the CAA have published an AIC detailing the new rules, but re-emphasising the same 8 hours absolute minimum which always used to be the guide-line. However, no one will guarantee that following these guide-lines keeps your blood-alcohol at a legal level.
FFF
-----------------