The story I was told Gingernut was that it was 5 pm at the Royal College of Physicians and the great and good had spent all day with the civil servants drafting a policy on alcohol. The doctors were keen to get to the bar but the civil servants refused to close the meeting until a safe limit had been agreed. In desperation the doctors pulled figures from the ether and disappeared to the bar
I suspect it has validity. Certainly the recommendations are rubbish with some people able to drink much more but others getting problems with lower levels.
Alcohol is the only vice that will prolong your life - if you drink regularly in moderation you will statistically have a greater life expectancy than if you are tee total. But equally drunks in city centres at 11pm and elsewhere cause massive harm and cost to society. As this posting shows it also causes anxiety in otherwise normal people. The debate is rather political - alcohol abuse does kill but whether the increase in incidence is as much as reported or merely reflects more accurate reporting is another debate