In the late 1990’s, much of Chester Castle walls had been closed to the public for safety reasons. The curtain walls therefore underwent a 15-year programme of progressive repair and conservation on a year-by-year basis. This involved very careful study of the existing fabric, followed by complex Scheduled Monument Consent procedures. Arrol Architects devised a new scheme of safety railings, access improvements, new paved walkways and drainage improvements, which allowed the wall walks and upper parts of the fortification to be reopened to visitors. A key aim of the project was to devise strategies for dealing with rainwater penetration and consequent stone decay problems. Great care was taken with stone selection and mortar design for all of the repair work.