There is a sense of inherent instability in something that is broader at the top than at the base. Convinced that it could be done, however, Ab Rogers called in engineer Chris Wise of Expedition Engineering. ‘Richard and I had an hour long meeting with him,’ Ab Rogers explained. ‘We asked, what could we do to make the ladder more dynamic and ambitious?’ The uprights of the ladder had to be designed so that they could provide handholds, since the person going up it needed something to hold onto as they turned and sat down. This has been resolved elegantly, with the upright having a tight outward curve at the top, and the other extending beyond the tray, which can fold away. A full-scale mock up in plywood was made at Benchmark to test stability and the feeling of safety.