In July 1941 an underground Medical Dressing Station (MDS) was constructed behind and above the Casemate level. When partially completed in January 1942 part of this MDS became was to become available for overflow accommodation for the Combined Services Headquarters being built below in what became known as Dumpy level.
When Dumpy level later became a Regional Seat of Government (RSG), the former MDS became dormitories and mess rooms for the site. Tours of this underground site are available as part of the normal visit to Dover Castle.