Within a few years of the completion of the Victoria Tower in 1860, the Anston magnesian limestone used for the Tower's external walls began to succumb to the smoky and acidic London atmosphere.
The building also began to suffer from erosion as a result of many blocks having been set in the wrong plane. By the 1920s, quite large fragments were falling off the Tower - and at least 198 tons of loose pieces had to be removed eventually.
Rebuilding the exterior
From 1926, a thorough rebuilding of the exterior of the Tower was consequently conducted by the Ministry of Works. This was an enormous and costly undertaking, and had to be discontinued during the Second World War.
The whole system of scaffolding was then dismantled and taken down to the beaches of the south coast, where it was erected as coastal defences, before returning to the Tower in 1946. The refacing of the Tower was eventually completed in 1953.
It was also realised after the war that much of the weight of the Tower in fact rested on the arch of the Royal Entrance in to the Palace, which was cracking under the strain. Huge steel girders were introduced, and the whole Tower was jacked up so as to rest on them.
Conservation during the late 20th century
In late 1988 and early 1989, a team of surveyors carried out a detailed inspection of the external masonry of the Victoria Tower using high-powered binoculars. The survey revealed that although the stonework was generally in a good condition, the build-up of pollution had taken its toll on various locations.
To restore the building, an intricate web of scaffolding was erected around the Tower. With its 68 miles of scaffold tube and some 125,000 fittings, it was one of the largest independent scaffolds in Europe.
Once the scaffolding was clad in protective sheeting, the interior of the Tower was connected to a mechanical ventilation and filtration system. This ensured that stable environmental conditions were maintained in the Archive's rooms throughout the process.