Red Squirrel Architects were commissioned by the London Wildlife Trust to design and implement a bat roost in Sydenham Hill Wood in South London. The site is within a disused railway tunnel which formed part of the Crystal Palace and South London Junction Railway which ran from Nunhead to serve the Crystal Palace (constructed in 1865). The design comprises of 2 parabolic steel frames with masonry in-fill which accomodates 24 artificial roosting boxes. These ‘hanging walls’ regulate temperature and humidity at the centre section of the tunnel. The presence of brown long-eared, and Natterer’s bats have been recorded and monitored within the railway tunnel. The project – funded by SITA Trust and supported by Southwark and Lewisham Councils – was completed in April 2009, and allows for future expansion of the number of roosting boxes.