Do you think he's really drinking ale in the show? In the Wolvercote Tongue he chugs a pint in less than a minute, if they had to shoot that seen more than once he would have been wasted... I'm not much of a beer drinker but he sure does make me crave a pint.
shareI did a bit of work as an extra a few years ago, and the beer used in a party scene was actual beer, but ultra low alcohol, and warm at that. We were asked to avoid drinking much of it to avoid continuity problems. I believe that whisky is usually cold tea.
You will notice that on TV people rarely get to actually eat on camera, or drink visible amounts of anything. Obviously there will be exceptions where the script demands it.