Rochester Castle Keep - The Exterior

A view of the keep from the south-east

The keep at Rochester Castle is one of the best preserved in England and France – as well as being one of the tallest - and although Bishop Gundulf had died by the time it had begun to be built in 1127, it is thought that it is modelled on the White Tower at the Tower of London, whose construction William I had ordered him to oversee.

A view of the keep from the east

Like the curtain walls, the structure is built entirely in Kentish ragstone except for the quoins and dressings, which are made from the yellowish coloured Caen stone – a Jurassic limestone from Normandy – and can easily be distinguished from the walling.

Caen stone window dressings with chevrons

Although both the English Heritage guide and a Conservation Plan refer to Reigate stone being used for the restoration of the keep after the 1215 siege, to my eye there is no evidence of a change of building stone from Kentish ragstone on the exterior. Both the colour and texture of the stone appears to be very uniform, except for the occasional incorporation of very dark flint into the masonry and, even where there are obviously darker sections, there appears to be more variation in the colour of the mortar than the stone itself.

A geological map of south-east England

Given the proximity of the principal source of Kentish ragstone in Aylesford/Maidstone, or a similar alternative from Folkestone – both of which have been used in the Tower of London – it is extremely unlikely that vast quantities of rubble stone would be moved 50 km overland, when supply routes by river and sea had long since been established.

A view of the keep from Baker's Walk

With just over 2 hours spent exploring Rochester Castle, I didn't have the time or reason to study any of the stonework in any kind of detail but I made sure that I had enough high quality photographs to enable me to make some of the above observations, and which would serve to illustrate various accounts of the castle that I would find during subsequent internet research – including an excellent report on its restoration by George Payne, an architect/antiquarian who was engaged to carry out various works from 1896 to 1904.

A break between original masonry and restoration after the 1215 siege

I didn't notice this at the time when walking around the exterior of the castle, partly because the elevation is obscured from Baker's Walk by trees, but there is a distinct break in the pattern of the masonry to the south elevation of the keep, which marks the extent of damage caused during the siege of 1215 and - looking at enlargements of general photographs of the masonry in the forebuilding – whole sea shells can be seen in the mortar.

Caen stone window dressings and mortar containing sea shells