A checklist to add to all the others. Assumption: the battery is good and the starter relay is not welded together.

Symptoms:

1. Turn on - the coolant light, oil light and generator light might come on. The main lights (headlight etc.) don't work.
2. If those three lights are on, hitting the starter button activates the starter relay and those three lights go out. No engine turnover. The fuel pump only runs as long as the starter button is pressed and stops as soon as the button is released.
3. Pulling fuse no.1 allows the main lights to work again but of course, no starter circuit.

Your killswitch has corrosion in it and is only making intermittant contact. Two unrecoverable hours to find that little smurf.

[Edit] An additional symptom is that you may get your coolant temperature light coming on for no reason when the headlights are on and you switch to main beam. I didn't originally list this because I wasn't sure if it was connected or not, but since I cleaned the killswitch that bit of irritation has also gone away.

2 hours?

You did good

Suggestion: Add "Start Kill Switch" to the title so people can find it when searching.

Duck: good idea - done.

Chris: that involved swapping out all the relays (including the starter relay), FICU and ICU to eliminate those before having to dig into the wiring. Having got that far with no results, I pulled, cleaned and reseated the connector block, after which the bike fired up once and refused again. I looked at it, figured out that of course I'd disturbed the wiring to the handlebar switch and so it had to be the killswitch: thus it proved to be.