This maisonette flat situated in a listed Victorian building in St John's Wood, was the subject of a partial modernisation which was to include a new glazed rear extension to provide a dining area and a den, whilst extending the lower ground floor to provide additional space for the master bedroom with a well-lit dressing room. The main challenges were to achieve a modern structure that had little impact on the character of the listed building and, secondly, the excavation of the lower patio to create the extended lower ground floor and deal with all the attendant problems of a subterranean extension. The results speak for themselves.