Excavation of basement storey beneath main house, demolition and rebuilding of mews house at new height plus the addition of a lower ground floor storey, demolition and rebuilding of main roof plus addition of plant equipment, erection of extension for lift from basement to third floor level, demolition and replacement of interconnecting extension between main and mews house, use of roof of interconnecting extension as a roof terrace, increasing height of boundary shared with 78 Chester Square and other external alterations as well as internal alterations throughout. (Linked with 22/05927/FULL)