The so-called Silly Walk Song by the Monty Python troupe (lyrics and video here, lyrics in text form here) is mostly a lament of the tedium and futility of a life of money-induced drudgery. But there are a few lines which are much darker and don't quite seem to fit with the tone of the rest of the song:
Life is a silly walk in the park,
A knife in your throat held after dark.
Life is a terrible joke a lark,
A spoken word then it all goes dark.
Where does the idea of a "knife in your throat held after dark" come from? What does it mean and how does it fit with the overall theme? What does bloody murder have to do with working uselessly in an office for money, or is there some indirect or symbolic meaning in this phrase?