What an amazing invention – I think this is one of the things that would be on my wish-list when I get a huge house big enough to fit my very own mini brewery and beer area (something I think every man should have)/

I wondered how the beer just doesn’t run right out of the bottom of the cup as soon as you pick it up. It seems there’s a disc-like thing at the bottom which allows the beer to flow up through the cup but which also acts as a seal to stop the beer running out.