The redevelopment saw the existing cellular room layout changed into an open-plan office layout to improve collaboration between staff and the working environment . All mechanical and electrical services were upgraded along with IT networks . New communal spaces were created including a library , restaurant , coffee shop , business & press suite and crèche . The internal courtyards were enclosed to create three new atria within the building . Security and anti-terrorism measures were integrated into the building , with the MOD changing such requirements after the 9/11 terrorist attacks . Original historic features of the building were protected and restored during the redevelopment , such as the replacement of oak doors and terrazzo marble floor of the Pillared Hall . All 2,494 metal windows in the building were refurbished and repaired
9/11 terrorist attacks
September 11 attacks
Ministry of Defence Main Building (United Kingdom)