This detached house in the Italian style previously known as Cato Lodge was built in 1851. Set within a Chelsea conservation area, it is unusual for London in that it is bordered on three sides by a walled garden. During the 1970's the house was the office and family residence of Post-War architectural doyennes Allison and Peter Smithson. During the time of their tenure the Smithsons ordered the house vertically with work and public spaces on the lower floors while the upper floors were reserved for family life. This programmatic order has been maintained and extended by the present owners who commissioned Lab Architects in 2011 to reconfigure the entire house and to extend it. The brief for this reconfiguration of extended space was to accommodate the clients extensive art collection and to include a swimming pool, gym and bedroom suites. The masterful sculpting of light wells which flood the spaces with natural light, coupled with vertiginous floor to ceiling heights are the key to the success of the basement. A grand bespoke stair, designed by Lab Architects, creates harmonious flow throughout the five floors of this elegantly remodelled residence. Photography: Joel Knight