From a talk by Mr. Chris Hunwick, the Duke of Northumberland’s Archivist.
Records have been stored at the Castle since at least 1443. Accounts were stored in the Exchequer Building, next to the Gatehouse, in an iron-bound chest. By 1557, the South-East tower had been constructed; this is now the Record Tower, which started as a rectangular building two storeys high. By 1608, there was another storey, and it had become semi-circular. Later it became a round tower with a top room, with wonderful views, designed by Robert Adam. Shortly after, the tower was altered again and restored to its medieval appearance.
The lower floor of this tower is now a basement, housing the automatic fire suppression system. When a fire breaks out, FN200 is released into the room, rapidly dropping the room temperature and suppressing the fire. The advantage of this system is that it causes no harm to the records, though people need to leave the room rapidly!
The top room of the Record Tower is of double height: it has a spiral staircase and gantry to access the upper shelves. Here, contract agreements have been stored for hundreds of years in bound bundles. Over the past 12 years, they have been taken out, carefully flattened, cleaned, and re-filed in acid-free folders. Other records, originally at Syon House, were stored in boxes. These are now also being repackaged, as the records are at risk of damage from acid leaching from the boxes. While this is being done, research can be undertaken on the contents, and the catalogue improved.
One of these pieces of research was undertaken for the 300th anniversary of Capability Brown’s birth in 2016. Unfortunately, there is very little original documentation left from Capability Brown himself. However, we do have maps from the 1780’s by the French cartographer, Claude Sauthier, who served with Earl Percy (later the 2nd Duke of Northumberland) in the American Revolutionary War. These can be compared with earlier maps to establish what alterations to the landscape Capability Brown made. Older maps show a patchwork of farms, with small, hedged fields, and the Aln had islands in its course. After landscaping, fields were merged, and the Aln was tamed.
There are a number of other useful sources. In 1875, P Waddell wrote a detailed account of a tour of the park, which does not seem to have been published, but which forms the basis of later accounts. It describes many changes, and discusses features such as the underground ice house, and the hidden culvert underneath a level green sward: this was washed out in 2012, and has since been replaced.
Another interesting source is a 1773 drawing showing a view of the medieval Aln Bridge with men working on the landscape. From all this information, an animation has been made to show how the landscape changed, and how they moved the many trees which were planted. This can be seen in Constable’s Tower.
Another piece of recent research has been undertaken into the Percy Tenantry Volunteers. Founded in 1798, there were both infantry and cavalry in anticipation of a perceived French attack which never materialised. When fighting in the American Revolutionary War, English soldiers wore red jackets and white trousers, making them highly visible. Earl Percy’s experience there led him to issue instructions the soldiers should wear green jackets, and that they should be trained in guerrilla warfare.