AJ 10.10.19: Leisure and retailThe latest AJ features building studies of Peter Zumthors Secular Retreat holiday home in Devon; Invisible Studios glazed gym at Hadspen House in Somerset; and Wright & Wrights Library and Study Centre for St Johns College, Oxford. PLUS The human cost of building Istanbul Airport we report from the construction site where at least 55 workers have died; we talk to Yvonne Farrell, co founder of Grafton Architects, awarded the 2020 RIBA Royal Gold Medal;