Yep, it's bloody brilliant (it being "I love Marijuana" by Linval Thompson). I've got it on a compilation, pretty sure it's the Lee Scratch Perry Arkology one.

My girlfriend is having her dub/reggae discovery period (oooer missus) which is a fantastic thing to view from afar as 3rd party. Like most people, she's started with the melodic Scratch Perry produced stuff, "Heart of the Congos" being her absolute favourite. But I got home the other day and she was listening to Keith Hudson, which is quite a step up in terms of dub-heaviness.