thanks for the link Brunno
did you notce that Marks uses middle pickup for intro and midlle solo ? first he switches wrongely on middle+neck and then immediately switches on middle
on chorus TV show he used bridge pickup for the solo. very rare !
on this video from old grey whistle test show, David's cable seems a lttle bit too short ! 
I'd noticed some interesting details, but if he starts the intro using the middle pickup, why would he switch back to middle for the first solo? Note that at no point does he show changing the pickup position before starting the first solo. This leads me to believe he uses bridge and middle in the intro and continues through to the first solo. He made a mistake by going middle and neck. As you noticed, after the first note, he immediately switches to the middle pickup and continues through to the end of the song using the middle pickup. That's how I noticed it: he starts with bridge and middle, and from the first solo onward, he uses middle.
Note that he wasn't even wearing wristbands yet. The coiled cables have a distinct vintage charm and were part of the band's sound until their second American tour in September 1979.
This song, in this context, is another great example of the importance of a rhythm guitar as firm and precise as the one David always mastered with such skill. It's so solid and efficient, little is said about it, but he had his own style and was perfect for the original quartet's sound. This sound is the sum of the four elements; the absence of one breaks this alchemy, as indeed happened when he left the band; everything sounded different. For me, this pure sound is unsurpassed. I admit I'm a purist, I don't deny it! 😅
