Songfacts®:

• One of the handful of songs written just before Joe Strummer joined The Clash (back when the formative group was known as the London SS), guitarist Mick Jones had the song written even before bassist Paul Simonon met him. "It (Protex) was the brand in all the pub condom machines, it was a valid subject for a song" Jones noted wryly.
  
  The song is laced with sniggery innuendo and is about a gent getting a condom in a pub toilet ("Money in my pocket gonna put it in the slot, open up the pack see what type I got") and pondering what exactly to use it for - the implication in the final verse being that it may be for his own purposes and not for use with a woman ("I don't need no skin flicks, I want to be alone").
• "Protex Blue" holds a notable position in The Clash's canon as being the opening song at their first ever show. After this it was never consistently in the band's live set, and appeared sporadically down the years, including with a dramatic return to their set in the 16 Tons tour in 1980 with a radical rearrangement including a new middle section.