I was genuinely stunned that one person felt the need to drink that much
I don't think he needed to it just crept up, back in the day a liquid lunch was the norm so say you had two pints at lunch and two at night I don't think you would have called yourself a heavy drinker, then add a couple on a Saturday afternoon watching the football and several on Saturday night on a night out even at 2 units a pint you are well into the 50 to 60 range and much more if the beer was stronger.