In 1932, the then new owner took over the grotto, and soon afterwards substituted electric lighting for the gas lighting that, over the decades, had blackened the once-colourful shells. Cleaning trials show that in the majority of the grotto the shells have lost their colour under the dirt and are white. The structure has also suffered the effects of water penetration, though was removed from the Heritage at Risk Register in 2012 after a five-year conservation programme, carried out in partnership with English Heritage. A scheme to sponsor replacement mosaic panels – The Roundel Project – was established in 2012.