The Wooden Structure within Royston Cave
Royston Cave can be split into two parts. The lower cave, decorated with carvings, is cylindrical and approx. 3 m high and 5 m in diameter, while the upper cave is empty of carvings, domed and a further 5 m tall. Both levels contain a number of holes, slots and niches.
In 1976, an excavation of the cave floor by Sylvia Beamon and Lisa Donel uncovered a post hole and two smaller holes about 300 mm apart, one of which contained a piece of decayed wood. This led to suggestions that there was originally a wooden structure inside the cave, perhaps in the form of a second floor, balcony or veranda.
Peter Houldcroft, manager of Royston Cave from 1990 - 2008, first linked the discovery of the floor holes with the numerous slots and niches in the upper cave. He used a simple plane table surveying device to create plan and panorama views of them (Figures 1 and 2) and used his background as an engineer to develop a possible appearance of the structure, based on the positioning and relationship of these slots.
Structurally, there are too few slots to support a balcony. The slots are also relatively superficial and not deep enough to support structural beams or a floor.
Instead, Houldcroft believed that the slots held beams intended simply as props to stabilise a free-standing structure in the centre of the cave. In this article, we will refer to this structure as the platform.
Houldcroft thought that the platform would likely have sat on a form of trestle; a framework, consisting of a horizontal beam supported by pairs of legs, which supports a flat surface such as a table top. The cave's trestle could have been simple corner braces (Figure 3) or something more elaborate. It may have had 3 or more legs but probably stood on 4.
The floor slot discovered by Beamon and Donel was recorded as being 1 m from the centre of the cave. If this hole was intended for the platform’s leg, additional leg holes would likely be on a 2 m diameter circle. Only part of the floor was excavated and no further excavation has been carried out, so no additional floor slots have been uncovered.
Houldcroft attributed the smaller holes found by Beamon and Donel to have been from the base of a ladder. The ladder would have allowed access from the centre of the platform to the lower cave below.
Houldcroft also thought that the platform would have supported the cresset, an oil burning lamp which hung beneath the East Shaft - thought to be a chimney to take away the smoke.
It’s unlikely the platform covered the entirety of the cave. There are no signs of contact with the chalk at platform level which suggests there was at least a small gap between the platform and the wall. Because the upper cave is domed, Houldcroft also deduced that an average-sized person wouldn’t have been able to stand nearer than about 1 m to the wall at platform level. This gives the platform a working area of approx. 3 m diameter. This would have still allowed access to the large niches in the upper cave, seemingly intended for storage, because of the curvature of the cave wall.
Various types and shapes of platform were considered and investigated by Houldcroft but he found it difficult to find a suitable arrangement of joists and planking.
Plan view of the upper cave reveals that the four niches and two shafts don’t seem to be randomly placed but are, on average, positioned at 60 degree intervals. Houldcroft discovered that two equilateral triangles, placed together in the centre of the cave to form a six-pointed star, could therefore be positioned so that each point hit each niche and shaft (Figure 4).
From this, Houldcroft surmised that the platform may have been shaped like a six-pointed Star of David although there is, of course, no definitive proof. Today, the Star of David is associated with Judaism but hexagrams have been used in various designs throughout history, including in medieval churches, and they’re not exclusively religious.
A 1:24 scale model was constructed in 1994 to illustrate what the structure may have looked like. The model is now exhibited in Royston Museum.
Slots and Niches
For reference, the slots and niches in Figures 1 and 2 are numbered clockwise starting from the North Shaft, except for Slots 12 and 13 which are higher up in the East Shaft.
Houldcroft believed that the slots were in groups that worked together; 1,2 and 8; 3 and 4; 5, 6 and 10; 7, 9 and 11; and 12 and 13, and that each group served a different function.
Slots 1 and 2 are directly above and below the natural bedding fault in the chalk, which the creators of the cave appear to have used as a reference point. Slot 2 is the only slot that doesn’t face towards the centre of the cave and sits at more of a tangent. There is also no slot opposite it. Houldcroft suggested that this meant the beam from Slot 2 passed under and attached to the beam from Slot 1.
Slot 1 is thought to have joined to Slot 8 to form the platform’s main horizontal crossbeam. This beam is likely to have been joined to the top of the trestle.
On the floor below Slots 1 and 8 are two tiles marking north and south. A compass shows that this is inaccurate by about 15 degrees but it certainly indicates that the positions of the platform and the cave held significance and may have been specifically aligned with the points of a compass. In the lower cave, a carving of St Christopher is at the northern end while St George stands to the south.
Slots 3 and 4 were initially referred to as ladder marks because they are about 30 cm apart. Houldcroft dismissed this theory and instead suggested that they supported two slats, hinged to the platform, which could be folded down when required. The slots are shallow and narrow so it seems unlikely that they carried any weight. As they are over ‘The Grave’ area, Houldcroft thought that they might have supported a device with ritualistic function, possibly like a decorative canopy.
Houldcroft thought that Slots 7, 9 and 11 were used to hold short lengths of wood wedged between the wall and the platform to stabilise it (Figure 5). There’s a possibility that these wedging struts were only used once the the structure had worn or rotted and become unstable.
Slots 5 and 6, below the East Shaft, and 10, directly opposite, are all just over 1 m above the bedding fault. Their purpose doesn’t appear to be to do with the platform. Houldcroft suggested that they could have held a Y-shaped structure which acted as a swivel for the cresset. This would have allowed the cresset to be lit while over the platform before being swivelled into place beneath the East Shaft.
In 1996, an investigation by English Heritage confirmed that Niche 1 was used to store oil for the cresset after discovering that the chalk there was stained brown, hard and brittle. This correlates with the effects of oil on chalk. Perhaps Niche 1a, immediately above, could have held the lid to cap the cresset and extinguish the flame when it was no longer needed.
Slots 12 and 13, on either side of the East Shaft, seem to have held a beam which Houldcroft believes supported a hood-shaped covering called a cowl, which is often seen above old chimneys. Its purpose would have been to make the East Shaft more effective at collecting the smoke from the cresset.
Elsewhere in the cave are a number of smaller holes which also appear to be original and man-made. Some possibly held rods to support candles to illuminate the carvings while others appear to have been created by nails, perhaps used to hold decorations in place. Most of the nails had rusted away before the cave was rediscovered but some, found during excavations, are exhibited at Royston Museum, although it is unclear whether these are original. A long line of holes running around the upper part of the cave, approx. 4.5 m from the floor, may have supported decorations such as hangings or flags.
What was the platform used for?
Considering there is such a distinction in the style between the upper and lower cave, it seems likely that the two levels would have had distinct functions too.
The lower cave is thought to have been religious, spiritual or ritualistic, while the upper cave appears to have had a more secular use. Perhaps it was used for storage, administration or preparation before descending below. From a purely practical point of view, the platform would have provided a landing for people entering the cave via the vertical North Shaft, as well as access to the upper storage niches.
If you’re interested in reading more about Peter Houldcroft’s theories on the platform, his publication ‘The Medieval Structure within Royston Cave’ is available to purchase from Royston Museum or Royston and District Local History Society.
Thank you to Royston and District Local History Society for their permission to use images from the publication in this article.
Beamon, S.P. and Donel, L.G. (1978). An Investigation of Royston Cave. Proceedings of the Cambridge Antiquarian Society. Volume LXVIII. Cambridge: The Burlington Press Ltd.
Beamon, S.P. (1992). Royston Cave: Used By Saints or Sinners? Baldock: Cortney Publications.
Houldcroft, P.T. (1995). The Medieval Structure within Royston Cave. Royston: Royston and District Local History Society.
Houldcroft, P.T. (1998). A Pictorial Guide To Royston Cave. Royston: Royston and District Local History Society.
Houldcroft, P.T. (2008). A Medieval Mystery at the Crossroads. Royston: Royston and District Local History Society.