The couch forms part of a ‘Linear Accelerator’: an X-ray apparatus used in cancer treatment. This couch example was the first of its type to operate above one million volts. It was used at St Bartholomew’s Hospital, pioneers in radiation therapy. Two different types of therapy are possible with the linear accelerator: X-ray or electron therapy. The machine targeted deep-seated tumours with a high intensity radiation beam (X-ray therapy) or treated superficial surface tumours with the electron beam (electron therapy). This caused minimal radiation to the surrounding tissue, preventing damage to healthy tissue. It was housed in a special basement treatment room over 12 metres below ground for maximum radiation protection. A moving floor meant patients could be positioned easily.