The British started work on the secret underground complex in 1940, during the siege of Malta, when a series of tunnels under the Upper Barrakka Gardens and the Saluting Battery that had been used as slave quarters during the Hospitaller period began to be expanded.

The Operation Headquarters at Lascaris communicated directly with radar stations around the Maltese islands, and it was equipped with Type X machines.

The Filter Room displayed information received from various places, including the naval station at Auberge de Castille.

The rooms closed down in 2005, but were acquired by Fondazzjoni Wirt Artna and the Malta Heritage Trust in 2009 and are once again open to the public.

[5] When ready, it is planned that the rooms will form part of a Military Heritage Park, including both the war rooms and the NATO Command Centre, as well as the SS Peter and Paul Counterguard, the Saluting Battery, and the crypt of the former Garrison Chapel.