Can't remember the exact number of floors, but many years ago I worked for a firm called "A.F.Cheese & Sons Ltd." We did only schools, all in the old ILEA (Inner London Education Authority). Some of the colleges were b****y high and we did them by "bosun's chair" - a single seat suspended from a rope hanging off a pole sticking out over the parapet. We had to rig it ourselves, so a two man team would work from a chair each. This meant one man on the ground would haul the first chair up to the roof. The man on the roof would climb down the rope, into the chair and then secure it so it couldn't slip down, and then climb back up to the roof. The man on the ground then hauled up the second chair and the one on the roof climbed down into it and started work, swinging from side to side as far as he could and lowering himself down floor by floor till he reached the ground. The man on the ground would go up to the roof and climb down into the first chair and start work as well, so both finished at roughly the same time, re-positioned the chairs and started all over again.
Climbing in and out of the chairs..................now
that was scary
Cheers,
Ian
PS this was before WAHD