Each open end of the tube offered a viewing platform to enjoy unique, focussed views of London. A segment of a 100m diameter circle, the Smile offered an immersive sensory environment integrating structure, surface, space and light. The Smile was prefabricated as 12 industrial-sized tulipwood CLT panels by CLT pioneers, Züblin-Timber in Germany. Up to 14m long and 4.5m wide, these were the largest ever to make it into production. We introduced perforations in the walls — concentrating where there is less stress on the structure and dispersing where the timber is working harder — to create a form of structural ornament, bringing dappled sunlight to the interior.

At night, when the interior was lit, the pavilion became a giant lantern. Arup applied their latest timber research to devise a structural connection system of 4000 screws over a foot long that can be installed with an ordinary rechargeable screwdriver. At the tube’s mid-span four 1m long steel plates connected the main structural panels at high level, also using screws. With 30,000 visitors and 290m online views, the Smile sparked a global audience through its pure form, its inventive use of material and its extraordinary engineering achievement.