The high Middle Ages saw the heyday of the French Borough when it became the wealthiest area of the city.

 

However, the area around Bethel Street saw little development in the thirteenth and fourteenth centuries. The southern and western parts of The Forum site were walled off by a flint and mortar wall and probably became part of the Hospital of St Mary in the Fields. This institution was established in 1248 and some of its buildings survive as part of the present-day Assembly House. The area within the walls themselves appears to have been used for some kind of gardening activity, perhaps an orchard or allotment.

 

The fifteenth and sixteenth centuries saw a renewal of intensive activity at the site, mainly well and pit digging. Much of the evidence for structures from this period had been removed during construction of the original library building in the early 1960s. These were timber-framed buildings with insubstantial foundations and were therefore easily demolished.