Originally the keep would have had a render of some sort covering the Septaria. On a big inspection a few years back the Septaria was found to be very worn in several places.
English Heritage have carried out several small test areas over the last few years to try to match the exact mix that would have been used (there are still lots to compare still in situ on the outer walls). The test patches have been left several years to weather down and they think they have found the mix.
Early last year they rendered a much larger patch and it is the first thing you see when walking up the path to the castle. This will be left in situ again to weather down and see if it is a good possible mix.
If so, they do intend to render the whole of the areas with Septaria in order to help the Castle to stand for future generations. This as you can imagine will be a very expensive project and we did have a board up about the work asking for donations to English Heritage purely for this project.
If they go ahead then it may be next year. It will give the Castle a whole new look, although it looks good with Septaria exposed it isn’t doing its longevity any good.