Black Box is a small first floor rear extension to a mid terrace Victorian era house in Islington, London. Our client, a professional couple, wanted a space that could function both as a home office and occasional guest bedroom with en suite bathroom. Situated on a dense urban site with neighbouring buildings in close proximity, any proposed extension would be overlooked from multiple sides – a typical London situation. At the same time, driven by a desire to maximize natural daylight provision and celebrate key views across adjacent gardens, we wanted the new space to benefit from large windows. We asked ourselves, can we introduce large glazing whilst regulating levels of shading, natural daylight, privacy, and security at different times of the day? The extension is conceived as a ‘reconfigurable box’ in dark stained Siberian Larch. Two bespoke counterbalanced shutters are manually operated internally using winches. These allow for multiple configurations of the ‘box; from fully open with window overhang to counter summer solar gain, to shut tight. The dynamic nature of the façade encourages the user to interact with the architecture and adapt their environment for comfort. The drawings show an extension at ground floor, an additional ‘black box’, that was designed together with the ‘black box’ at first floor (and approved under the same planning application). The client chose to phase the implementation of this scheme with the first floor element being delivered first and the ground floor component to follow at a later date.