The clients for this project sought planning permission for a new house within the garden of their current home. There was however a presumption in local policy against the development of back gardens and two previous planning applications had been refused. Moreover, the property is located in a highly-sensitive location being both within the Mortlake Conservation Area and very visible from the public realm. We advised on a strategy to address these challenges. Working with architects Dallas-Pierce-Quintero, a design was developed for a “hidden house”. We recommended replacement of the existing modern fence with a high-quality reclaimed brick wall that would both provide an enhancement to the conservation area and allow the new house, which was sunk by 0.8 metre into the ground, to be hidden behind it. We proposed an extensive green roof in order to safeguard the verdant outlook from neighbouring properties.There were no objections from neighbours and the application was approved by the local planning authority.