Gunpowder production began at Waltham Abbey in the mid-1660s and the site subsequently developed into the pre-eminent powder works in Britain and one of the most important in Europe. The Royal Gunpowder Mills were at the forefront of developing and producing explosives until WW2, when production ceased due to the site's vulnerability to air raids. After the war it became the principal government research establishment for non-nuclear explosives and propellants. The site was eventually decommissioned in 1991 after some 330 years of activity. The importance of the vast 91 hectare site was quickly recognised and surveys by the Royal Commission led to over two thirds of the site being designated as a Scheduled Ancient Monument (SAM). Outside the SAM are 21 individually listed buildings. The site is isolated by two major watercourses and this, coupled with the gradual abandonment of the site and the spread of the Alder trees (originally planted for coppicing to make charcoal) had led to a rich ecosystem and a designation of 34 hectares as a SSSI. Thomas Ford & Partners were appointed in competition as architect and lead consultant for a major project to open the historic site to the public for the first time in its history. Our work included condition surveys of some 300 surviving buildings and structures, conservation of the most vulnerable buildings and the restoration and alteration of five major buildings to form a visitor reception and orientation centre, exhibition gallery and lecture theatre, restaurant, research centre and display areas. The majority of these buildings are listed either Grade 2* or Grade 1. Site-wide works include extensive boardwalks, landscaping, car parking and interpretation, together with major infrastructure works to provide services and access. Disabled access a key issue for both buildings and the site generally. A high level of consultation was necessary, involving the local and county councils, English Heritage, English Nature and the Environment Agency. A major part of our work was located at the southern end of the site where a number of listed buildings are situated within the SAM. This part of the site houses the main exhibition building and lecture theatre - the new entrance to which was to be situated between two Grade 2* and one Grade 2 listed building. We faced the interesting challenge of designing a new entrance which was a prominent arrival point and yet not in conflict with the important historic buildings and the Scheduled Monument. Elsewhere we undertook a programme of research into the curious original construction of the only Grade 1 listed building, prior to removing later additions and restoring the building to an earlier form. It is now possibly the only building in Britain with felt paneled walls! The practice led a full team of consultants, working closely with the project manager and with exhibition designers and ecologists appointed directly by the client.