Wiring conundrum

getting S3 on road after few months.
Replaced solenoid finally.
However getting no spark - done usual simple tasks, cleaned gapped plugs, cleaned dizzy, rotor arm and points good condition.
What I have noticed is that I have errant black wire! Should this be connected to something "starting related?" Or is it another Landy phantom wire?
See attached photo - relevant wire on end of Sharpie
Any ideas welcom
Ta
Tom

Don't know.... But the fact it doesn't spark would make me first check there's no power on it, then earth it to see if the spark comes back. What's on the other end of the wire?