sorry to say this, but anyone going 40 foot up on a ladder these days needs his head testing.
Just say 'no, i can't do that'. Unless you've got wfp or a harness connection to the building.
Being 40 foot up on a ladder doesn't make you a better windowcleaner than the guy on the ground floor, nor does it pay better in the long run.
We're trying to make a living here, not kill ourselves for a few quid.
I hope the guy who fell recovers, but 40 feet through glass!!!
Pj