wightsurf
Ive had a couple of blokes work for me in the past.
one stepped of a flat roof , he forgot where he was and the window edge was past edge of roof.he just stepped off,luckely his fall was broken by a plant pot.one broken arm.As for ladders, woods the best they give you warning before snapping.As for slipping common sence works quite well.
Although i use mostley wfp now.