Little is known of its function beyond its name and the discovery of poppy heads in the rafters. It was presumably to store and dry herbs for the Hospital's apothecary. At about the same time as the Operating Theatre was built the roof was reroofed and dormer windows inserted. It has been conjectured that this may suggest the Garret changed use and perhap became a recovery ward.
In 1862 the Hospital moved, and the Garret and Operating Theatres were closed down.
It is now part of the Old Operating Theatre Museum and Herb Garret, Southwark and was put back into public use in 1962