The effect of beer on your English proficiency:-

One pint: no change in your English .
Two pints: your English goes up a level.
Three pints: your English goes up a level, but your grammar disappears.
Four pints: you become very fluent, but start mixing English up with your own language.
Five pints: you discover that you can sing in English and are brilliant at karaoke.
Six pints: you suddenly know lots of taboo words in English (fortunately, no one else seems to understand them)
Seven pints: you can`t speak English at all, and you also forget your own language.
More than seven pints: you`ve reached the danger zone – you start speaking American English.

From “The How to Be British Collection” by Peter Legon and Martyn Ford

Thanks to Hermine