Erection of extension in roof valley and lift extension at main roof level, new plant atop roof extension, replacement of areas of glazed roof in rear lightwell, formation of a ground floor level terrace and new doorway within rear lightwell. Replacement of rooflights, doors and windows to mews. Internal alterations, including installation of plant within the vaults, new areas of suspended ceiling and service risers, removal of partitions and formation of new openings in existing partitions. Retrospective consent for opening up works. (linked to 21/00188/FULL).