The intention was that it should serve as an Emergency Medical Service hospital for local air raid casualties. This proved unnecessary, and on the completion of the buildings in January 1942 they were leased to the medical services of the United States Army.

The American Hospital in Britain was invited to take over the hospital in September 1941, under the general administration of the Wingfield-Morris Orthopaedic Hospital (now the Nuffield Orthopaedic Centre). They transferred their activities from Park Prewett Hospital, Basingstoke, on 1 January 1942.

The hospital was opened as the Churchill Hospital by the Duchess of Kent on 27 January 1942. It was the 2nd General Hospital under Colonel Crawford July 1942 - April 1944 and then the 91st General Hospital under Colonel Dyke.

The video below, which has no soundtrack, shows archive footage of Her Majesty Queen Elizabeth The Queen Mother visiting the Churchill Hospital on 26 July 1944.