David Mitchell pissed in a drawer of a credit control agency?

Hey so I'm working on a YouTube video about peep show and came across one particular fact about David Mitchell pissing in a draw in a credit control agency. Initially i thought it was referring to the episode in which Davids character, Mark, does this and this was actually David Mitchell pissing into the drawer in the scene and not, for a lack of a better phrase, prop piss. however I then came across an article in the guardian where Sam Bain talked about his favorite scene of each season, and said when writing the episode Das Boot, they used Davids inability to drive as inspiration for the conflict in the episode. But then he goes on to say that this isn't the first time they have taken inspiration from David for the writing of his character, as he states, "It's a lesser-known fact that David also once pissed in a drawer at a credit control agency."

Does anyone have a bit more information about this because this quote is all I can find on the subject, and would be nice to have a bit more detail in the video. Goodwill to all men!