An account of emergency structural repairs made to the floor of the Long Parlour of the Mansion House (London) over a five week period during the summer of 1983. Author describes the house and the room, and discusses the methods used to study the floor's structural problems and the conclusions drawn from that study: the floor was under designed, inherently weak, poorly repaired, progressively springy and sagging. He summarizes the sequence of repair work in a table, and comments in detail on several parts of the work-steelwork, main beams, resin work, Entrance Hall, plasterwork, chimney piece.