I remember working on the Emley Moor mast about 30 years ago. We were doing a full 'hands on' examination of the concrete, both inside and out.
The longest drops you could do without being blown away from the structure too much was about 50m. The aircraft warning lights are spaced at 50m so we carried out a mechanically bolted aid climb all the way around the mast at each 50m level and rigged twin horizontal traverse lines so the examiners could easily aid climb out to the required drop point, abseil down to do the examination, and then get off at the next level down. There is a lift to get you back up a level.
My work colleague for the rigging element of the job, and a very experienced caver, climbed out of the aircraft warning light door at 200m with his drill, ropes and bolting gear only to return again a few minutes later saying it was too high for him and he would do the internal work instead. That left me to rig the horizontal routes at the 200m and 250m aircraft warning lights. From the 250m level I then had to climb vertically for nearly another 50m and then rig another horizontal route around the underside of the control room at nearly 300m.
I then had to de-rig it all a few days later. De-rigging the top section was particularly hairy as the anchors were gradually removed, leaving me with just 2 anchors to do a 'pull-through' down to the 250m level.
We had some spectacular mornings with the clouds below us and we regularly saw aeroplanes flying below us.
I was the contracts manager for a Canadian rope access company in 1997 and we carried out the first ever 'hands on' examination of the aerial at the very top of the 553m CN Tower in Toronto. It had only ever been examined through binoculars from a helicopter. We could only carry out the examination in the very early hours of the morning, as they had to switch off all the transmitters, so we didn't get the best views. We'd hoped to be able to use some of the photographs of the job for our company brochure but they made us hand over all our camera film after the job for security reasons.
The Emley Moor job is still one of the best rope access jobs ive ever done. I got quite proficient at aid climbing and did a lot of underground climbs around that time.